根据神经纤维直径粗细及来源，将传人纤维分为
A．A类B．B类C．A、B、C三类D．Ⅰ、Ⅱ、Ⅲ、Ⅳ四类
参考答案：D
函数f（x）=（x-2）2，则f′（1）=（ ）
A．-2
B．2
C．1
D．-1
—It _____ Yang Liwei about 21 hours _____ around the earth 14 times in the spaceship.
—How great he is! [ ]
A. spent, moving
B. took, traveling
C. took, to move
D. spent, to travel
