角钢塔整体中心垂直倾斜度要求不大于（）。
A、1/750
B、1/1000
C、1/1500
D、1/2000
参考答案：C
电流表不允许直接接在电源两端，这是因为电流表的____非常小，这样做会使电路中产生很大的电流将电源和电流表烧坏。
This year the number of the US students ____in China has increased by 18.4percent compared to last year.
A． to study
B． studying
C． having studied
D． studied
