The main advantage and chief characteristic of a Steulchen boom is that it can be（）.

A.operated by one winchman

B.cradled on deck

C.swung from one hatch to the adjacent hatch

D.collared to the mast

采购食品添加剂应当查验供货者的（）和产品合格证明文件。

A.营业执照

B.许可证

C.检验报告

D.自查报告