由一种材料制成的绞合导体，它的线膨胀系数一般与单线线胀系数（）。
A.大
B.小
C.相同
D.不同
参考答案：C
设命题p：实数x满足x2-4ax+3a2＜0，a∈R；命题q：实数x满足x2-x-6≤0，或x2+2x-8＞0，
（1）求命题p，q的解集；
（2）若a＜0且¬p是¬q的必要不充分条件，求a的取值范围．
Tom as well as his friends ____ to visit our school soon after they arrive in Nanan.[ ]
A. is coming
B. are coming
C. will have come
D. has come
