They each carried__________ on their backs.

A．so big an equipment

B．a such big equipment

C．so a big piece of equipment

D．such a big piece of equipment

工程师接到通知后，可与承包商商定竣工检验的日期，或决定并通知承包商在该日期后的( )天内的某日或数日内进行竣工检验。

A．7
B．14
C．18
D．21