体温节律性变化的周期
A．稍短于12小时
B．稍长于12小时
C．稍短于24小时
D．稍长于24小时
参考答案：D
-The food is very delicious. I'm very full.
-Why don't you ______ a walk with me?[ ]
A. take
B. to take
C. takes
D. took
我国电力的标准频率是（）Hz。
A、220
B、110
C、60
D、50
