钢丝绳外层钢丝磨损量超过原直径的()%应该报废。
A.50
B.40
C.30
D.20
参考答案:B
当a+4.2=5.1,b+a+2.3=15.9时,b=12.7.______.(判断对错)
—Where is Zhang Ming?
—Oh,he ______to Beijing to see his parents and he'll be back tomorrow.[ ]
A. has gone
B. has been
C. had gone
D. had been