黄铜接头焊接应采用（）火焰较为合适。

A.中性略偏炭化火焰

B.中性略偏氧化火焰

C.氧化略偏碳化火焰

D.炭化火焰

Woman: Bill, I want to have a few words with you about your performance in class lately.

Man: I know I’ve gone down. I just haven’t been studying as much as I ought to.

Question: What is Bill’s problem().

A. He doesn’t like to perform in class.

B. He doesn’t work hard enough.

C. He has gone away lately.

D. He feels depressed.