[请教]大全9-3 没人问过

dogholiday

大全9-3

The National Transportation Safety Board has recommended the use of fail-safe mechanisms on airliner cargo door latches assuring the doors are properly closed before takeoff and to prevent them from popping open in flight.

a. assuring the doors are properly closed

b. for the assurance of proper closing

c. assuring proper closure

d. to assure closing the doors properly

e. to assure that the doors are properly closed (e)

请教一下recommend 和assure的用法，谢谢！

dogholiday

自己顶一下