Not until all the fish died in the river _____ how serious the problem of water pollution was. [ ]

______ has recently been done to provide more buses for the people, a shortage of public vehicles remains a serious problem.

There are three______ workers in this factory. My brother is in it ,too.

You_______ so badly now if you had taken the medicine yesterday.

You don’t know ________ I want to see you again. It’s years since I saw you last time.