If you really have to leave during the meeting, you’d better leave _________ the back door. ..

If you really have to leave during the meeting, you’d better leave _________ the back door. ..

B

B。by在此表示“通过”，如：The thief slipped out by the back door. 那个贼偷偷(从后门)溜出去了。这样用的by用through用法相同，有时可互换，如：The burglar got into the house by / through the bedroom window. 窃贼是从卧室的窗户潜入这所房子的。