The gym is a public place, so you should be ________ and leave all the machines clean after using them.
The old sick lady entered the hospital, ______ her two sons.
_______ many times, he still couldn't understand.
Many things _______ impossible in the past are very common today.
The students in the university are all taking courses _______ a degree.
. _______ different kinds of pianos, the workers farther improved their quality.