Yesterday, when I went to his office, he ______ online for some information. I think it will be an interesting lecture.
He must have passed this way, _____here are his footprints.
“Why can’t you do it now?” “_____I’m too busy.”
_____it is raining, we had better take a taxi.
It was_____he was ill that he was absent yesterday.
_____everybody is here, Let’s set off.