I find there ______ no pencils in my pencil case.[ ]
A. is
B. are
C. be
D. have
答案:B
Computers in offices and homes since 1970s.
A.have been used
B.had been used
C.was
D.has been used
用对角线法测量平面度时,由于布线的原因,在各个方向测量时应采用()垫块。
A.相同长度
B.不同长度
C.规定的长度