测定煤中灰分时，炉膛内要保持良好的通风状态，这主要是为了将（）排出炉外。
A.水蒸气；
B.烟气；
C.二氧化碳；
D.二氧化硫和三氧化硫。
参考答案：D
I am considering changing to a more interesting job, as the present job, which requires a lot of _______, nearly bores me to death.
A．repetition
B．instruction
C．impression
D．appreciation
