Children aren't _____ out during their free time. But more and more parents know it's not good for the

children's health.        [ ]

A. allow go                      

B. allowed to go

C. allowed going                  

D. allowecl co go to

旋（扳）转法竖立桅杆时，可以利用后背的（）高度，也可以利用吊车或头部辅助扒杆，起吊桅杆头部，进行辅助抬头。

A、辅助扒杆

B、地面地锚

C、已有高大建构筑物

D、高设备