So many problems! I’m tired.—You should try to _________ them by yourself. You are not a child any longer.

Why do you look so worried- My MacBook Pro broke down and mypaper______unfinished since.

They have _____ most carefully the time and money needed to complete the project.

_______such heavy pollution already, it may now be too late to clean up the river.[ ]

He reminded me of what I should ______ haveforgotten.