Remember everybody you meet online is a stranger.So when you can’t see a person, they could be ________.
Can you explain ________ the sun goes down in the west?
—Someone has tidied the sitting room! —Jim __ it this morning; he couldn't bear the mess any more.
Peterson used to work in a remote mountain village school, which is only on foot.
I would appreciate ______ very much if you help me with my English.
Only by practicing a lot _____ our English well enough to communicate with foreigners.