_______ for months to find a job as a cartoon maker, John finally took a position at a local advertising

agency. [ ]

A. Struggling

B. Struggled

C. To struggle

D. Having struggled

火区封闭时为了便于隔离火区，应首先封闭或关闭（）。

A、向火区供风的旁侧风道

B、回风侧的防火墙

C、向火区供风的主要通道

D、进风侧的防火墙