【单选题】用万用表测量电阻时,选择好合适的档位后,应先( ),再测量
【单选题】Nobody’s answering the door. They ___________ be out.
【单选题】It's still early in the morning. There isn't______in the office.
【单选题】Since nobody is answering the phone, they ______.
【简答题】Nobody's answering the door. They ________ be out. (can/must)
【单选题】She can't help______the report because she's busy answering phones.