diff --git a/index.html b/index.html
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--- a/index.html
+++ b/index.html
@@ -275,7 +275,7 @@ const Q = [
 {"id":"c96","src":"真题","sub":"chinese","ch":"热身圈","topic":"错别字","type":"fill","stem":"改正下列词语中的错别字：\n前扑后继( ) 拾金不味( ) 愤不顾身( )\n无可耐何( ) 文丝不动( ) 迫不急待( )","opts":null,"ans":"扑-仆,味-昧,愤-奋,耐-奈,文-纹,急-及","exp":"前仆后继、拾金不昧、奋不顾身、无可奈何、纹丝不动、迫不及待。"},
 {"id":"e1","src":"真题","sub":"english","ch":"热身圈","topic":"be动词","type":"choice","stem":"Five and seven ___ twelve.","opts":["C. is","B. are","A. be","D. am"],"ans":0,"exp":"5+7=12是一个整体概念（一个数），用is。"},
 {"id":"e2","src":"真题","sub":"english","ch":"热身圈","topic":"冠词","type":"choice","stem":"Mr. Wang is ___ excellent teacher.","opts":["A. a","D. /","C. the","B. an"],"ans":3,"exp":"excellent以元音音素/e/开头，用an。"},
-{"id":"e3","src":"真题","sub":"english","ch":"热身圈","topic":"冠词","type":"choice","stem":"Do you like playing ___ piano? - No, I like playing ___ chess.","opts":["A. a, the","D. the, a","C. /, the","B. the, /"],"ans":3,"exp":"乐器前加the（piano），球类/棋类前不加冠词（chess）。"},
+{"id":"e3","src":"真题","sub":"english","ch":"热身圈","topic":"冠词","type":"choice","stem":"Do you like playing ___ piano? - No, I like playing ___ chess.","opts":["A. a, the","D. the, a","C. /, the","B. the, /"],"ans":3,"exp":"乐器前必须加the：play the piano（弹钢琴）。球类/棋类前不加冠词：play chess（下棋）。规律：play + the + 西洋乐器，play + 球类/棋类（零冠词）。"},
 {"id":"e4","src":"真题","sub":"english","ch":"第一赛段","topic":"代词","type":"choice","stem":"My cousin gave ___ a cute teddy bear for my birthday.","opts":["C. me","B. my","A. I","D. mine"],"ans":0,"exp":"gave后接宾语，用宾格me。"},
 {"id":"e5","src":"真题","sub":"english","ch":"第一赛段","topic":"介词","type":"choice","stem":"John starts work ___ 10 o'clock every day.","opts":["C. at","B. on","A. in","D. for"],"ans":0,"exp":"at+具体时间点。at跟点，on跟天，in跟月年。"},
 {"id":"e6","src":"真题","sub":"english","ch":"第一赛段","topic":"一般现在时","type":"choice","stem":"My mother often ___ after supper with my sister.","opts":["A. is taking a walk","B. take walk","C. takes walks","D. takes a walk"],"ans":3,"exp":"第三人称单数（My mother），often表经常，用一般现在时，动词加s。take a walk固定搭配。"},
@@ -318,7 +318,7 @@ const Q = [
 {"id":"e87","src":"真题","sub":"english","ch":"热身圈","topic":"语音","type":"choice","stem":"找出划线部分读音不同的选项：A. seat B. read C. sweater D. bean","opts":["A. seat","B. read","C. sweater","D. bean"],"ans":2,"exp":"seat/read/bean的ea发/i:/，sweater的ea发/e/。"},
 {"id":"e88","src":"真题","sub":"english","ch":"热身圈","topic":"语音","type":"choice","stem":"找出划线部分读音不同的选项：A. give B. like C. bike D. Mike","opts":["A. give","B. like","C. bike","D. Mike"],"ans":0,"exp":"like/bike/Mike的i发/aI/，give的i发/I/。"},
 {"id":"e89","src":"真题","sub":"english","ch":"热身圈","topic":"语音","type":"choice","stem":"找出划线部分读音不同的选项：A. with B. thank C. think D. month","opts":["A. with","B. thank","C. think","D. month"],"ans":0,"exp":"thank/think/month的th发/θ/，with的th发/e/。"},
-{"id":"e100","src":"真题","sub":"english","ch":"热身圈","topic":"冠词","type":"choice","stem":"Do you like playing ___ piano? — No, I like playing ___ chess.","opts":["A. a, the","B. the, /","C. /, the","D. the, a"],"ans":1,"exp":"乐器前加the(弹钢琴)，球类/棋类前不加冠词(下棋)。"},
+{"id":"e100","src":"真题","sub":"english","ch":"热身圈","topic":"冠词","type":"choice","stem":"Do you like playing ___ piano? — No, I like playing ___ chess.","opts":["A. a, the","B. the, /","C. /, the","D. the, a"],"ans":1,"exp":"乐器前必须加the（play the piano），球类/棋类前不加冠词（play chess/play basketball）。注意：西洋乐器加the，中国乐器（如play erhu）是否加the有争议，但小升初只考西洋乐器。"},
 {"id":"e101","src":"真题","sub":"english","ch":"热身圈","topic":"冠词","type":"choice","stem":"There's ___ interesting book about animals in my bag.","opts":["A. a","B. an","C. the","D. /"],"ans":1,"exp":"interesting以元音音素开头，用an。泛指一本有趣的书。"},
 {"id":"e114","src":"真题","sub":"english","ch":"热身圈","topic":"介词","type":"choice","stem":"We usually go to school ___ bus.","opts":["A. in","B. on","C. by","D. with"],"ans":2,"exp":"by+交通工具，by bus坐公交车。"},
 {"id":"e115","src":"真题","sub":"english","ch":"热身圈","topic":"介词","type":"choice","stem":"My sister was born ___ the morning of May 1st.","opts":["A. in","B. on","C. at","D. for"],"ans":1,"exp":"具体某一天的上午/下午用on。"},
@@ -489,7 +489,7 @@ const Q = [
 {"id":"m349","src":"真题","sub":"math","ch":"最终圈","topic":"找规律","type":"fill","stem":"按规律填数：1, 4, 9, 16, 25, （ ），（ ）。","opts":null,"ans":"36,49","exp":"规律：第n个数是n²。1=1²，4=2²，9=3²，16=4²，25=5²，6²=36，7²=49。"},
 {"id":"m350","src":"真题","sub":"math","ch":"最终圈","topic":"找规律","type":"fill","stem":"按规律：第1个图有4个棋子，第2个图有7个，第3个图有10个。第n个图有（ ）个棋子。","opts":null,"ans":"3n+1","exp":"每次增加3个。第1个=4=3×1+1，第2个=7=3×2+1，第n个=3n+1。"},
 {"id":"m351","src":"真题","sub":"math","ch":"最终圈","topic":"找规律","type":"choice","stem":"一张纸对折1次有2层，对折2次有4层，对折3次有8层。对折n次后有（ ）层。","opts":["A. 2n","B. n²","C. 2ⁿ","D. n+2"],"ans":2,"exp":"对折1次=2¹层，2次=2²，3次=2³，n次=2ⁿ层。指数增长规律。"},
-{"id":"e301","src":"真题","sub":"english","ch":"热身圈","topic":"冠词","type":"choice","stem":"Do you like playing ___ piano? No, I like playing ___ chess.","opts":["A. a, the","B. the, /","C. /, the","D. the, the"],"ans":1,"exp":"乐器前加the（play the piano），球类/棋类前不加冠词（play chess）。"},
+{"id":"e301","src":"真题","sub":"english","ch":"热身圈","topic":"冠词","type":"choice","stem":"Do you like playing ___ piano? No, I like playing ___ chess.","opts":["A. a, the","B. the, /","C. /, the","D. the, the"],"ans":1,"exp":"乐器前必须加the：play the piano。球类/棋类前不加冠词：play chess。excellent以元音音素开头用an，university以辅音音素开头用a。"},
 {"id":"e302","src":"真题","sub":"english","ch":"热身圈","topic":"冠词","type":"choice","stem":"There is ___ apple and ___ orange on the table.","opts":["A. a, a","B. an, an","C. an, a","D. a, an"],"ans":1,"exp":"apple和orange均以元音音素开头，用an。"},
 {"id":"e303","src":"真题","sub":"english","ch":"热身圈","topic":"冠词","type":"choice","stem":"My father is ___ engineer. He works in ___ university.","opts":["A. an, a","B. a, a","C. an, an","D. a, an"],"ans":0,"exp":"engineer以元音音素开头用an，university以辅音音素/ju:/开头用a。"},
 {"id":"e304","src":"真题","sub":"english","ch":"热身圈","topic":"冠词","type":"fill","stem":"用a/an/the填空（不填的写 /）：\n(1) ___ sun rises in ___ east.\n(2) I have ___ cat. ___ cat is black.\n(3) She is ___ honest girl.","opts":null,"ans":"The,the,a,The,an","exp":"(1)太阳/东方是独一无二的，用the。(2)首次提及用a，再次提及用the。(3)honest中h不发音，以元音音素开头用an。注意the sun/the east的固定用法。"},