问题
选择题
---What do you think of French?
---In my opinion, French is _______ English.
A．a subject so difficult as
B．as a subject difficult as
C．as difficult a subject as
D．difficult as subject as
答案
答案：C
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，当传送带分别以
的速度做逆时针转动时（
）绳中心的拉力分别为F1、F2，若剪断细绳时物体到达左端的时间分别和
，则下列说法正确的是（ ）
