单项选择题

The police wanted Dan to call at the station. They wanted him to call ______ them.
A、at
B、in
C、on
D、up

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多项选择题

关于开环、闭环控制说法错误的是：（）A、开环控制抗干扰能力强B、闭环控制中控制作用于输出无关C、闭环控制抗干扰能力强D、开环控制中控制作用于输出无关

In accordance with international usual practice, buyers are only responsible for special insurance charges.
正确
错误

答案：正确