I’ll sleep with the window open it’s really cold.

It’s certain that we are ________ to having a clean and beautiful home in the future because some special projects are ________ to protect the environment.

ld convey my appreciationto my high school teachers, without ____ help I wouldn’tachieve such a big success.

All _____ can be done has already been done.

_____must I take this medicine everyday— Three times a day.