国标中生活在屏障环境中的大、小鼠的温度范围是（）
A.18—23℃
B.23—28℃
C.20—26℃
D.20—28℃
参考答案：C
A waiter works _____________ a restaurant. [ ]
A. on
B. at
C. in
D. to
There are three _________ sheep on the farm.
A．thousand
B．thousands
C．thousand of
D．thousands of
