My brother has been preparing carefully for the English exam, so that he can be sure of passing it at his

first _____. [ ]

A. request

B. attempt

C. promise

D. purpose

立式罐的防火墙实高不应低于Im，防火墙内应为不燃材料铺设的地坪，防火墙内有效容量应为（）容量。