下列哪一型神经纤维的传导速度最快
A．A纤维
B．B纤维
C．C纤维
D．D纤维
E．E纤维
参考答案：A
（-5a2+4b2）（ ）=25a4-16b4，括号内应填（ ）
A．5a2+4b2
B．5a2-4b2
C．-5a2-4b2
D．-5a2+4b2
The group is made up____five students. And they are studying hard to make up____ the lost time.
A．of,of
B．for,for
C．of,for
D．for,of
