问题
单项选择题
The accuracy of scientific observation and calculations is always at the mercy of the scientist's timekeeping methods.
A．under the control of
B．within the kindness of
C．beyond the reach of
D．out of the control of
答案
参考答案：A
解析：[分析] 固定搭配 at the mercy of表：受……支配；而选项A．under the control of受……的控制；因此A为答案。