当变风量空调系统的送风干管静压升高到一定程度时，就要（）送风机的转速，以减少总送风量。
A、升高
B、不改变
C、降低
参考答案：C
He looked under ______ table and found ______ pen he lost the day before yesterday. [ ]
A. the; a
B. the; the
C. /; the
D. the; /
—"______ ?"
—"March 12th."[ ]
A. What time is it
B. When is your birthday
C. What do you do
D. Is it your birthday
