【简答题】发动机润滑油的功能有哪些?机油品质的检验方法?
【单选题】若对某角观测一个测回的中误差为±3′′,要使该角的观测精度达到±1.4′′,需要观测( )个测回。
【单选题】When he caught a _______ of his girl-friend in the rain, Jack asked the taxi driver to stop to pick her up.
【简答题】国家标准规定了两种等效的配合基准制:________和________。
【单选题】When he caught a ( ) of his girl-friend in the rain, Jack asked the taxi driver to stop to pick her up.