起重作业应由（），分工明确。
A.专人指挥
B.现场负责人指挥
C.安全监护人
D.施工队长
参考答案：A
(2013·福建，34)Not until he went through real hardship ________ the love we have for our families is important.
A．had he realized
B．did he realize
C．he realized
D．he had realized
( )是质量的法定计量单位。
A．牛顿
B．吨
C．千克
D．斤
