问题描述：
( )I am,weak in English.I don't know _.
A.what to improve B.how can I improve it C.how improve D.howI can improve it.
( )Millie can't ride a bike very well.Please don't jump on her bike suddenly while she is riding,or she will _.
A.fell down B.felled down C.felt down D.fall down
A.what to improve B.how can I improve it C.how improve D.howI can improve it.
( )Millie can't ride a bike very well.Please don't jump on her bike suddenly while she is riding,or she will _.
A.fell down B.felled down C.felt down D.fall down
问题解答：
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