应急电源的工作时间应按生产技术要求的停车时间考虑,当与自起动发电机组配合使用时,不宜小于()。
A.30min
B.20min
C.10min
D.5min
参考答案:C
笔算加法和减法时,相同数位要______,从______加起或减起.
Are you going to buy some _____? [ ]
A. food and drinks
B. foods and drink
C. drinks and snacks
D. drink and snack