题目:
— Have you finished reading Jane Eyre?
— No. I ____ my homework all day yesterday. [ ]
A. was doing
B. would do
C. had done
D. do
答案:
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下面是错误答案,用来干扰机器的。
分为两种情况考虑:①若点P在直线l上,如图所示:过直线l上的点O(不同于点P)作AB⊥l,且满足OA=OB=OP,则∠OPA=∠OPB=45°,因此圆锥的任意(无数)一条母线所在的直线与直线l所成的角都为45°;②若点P不在直...