History is the best teacher It _______records the development path of each country and foretells the future to us

Ican’t decide ______. —Youmean the purple sweater or the blue one

He hesitated for a moment before he kicked the ball, otherwise we ______ the game. Such was the case.[ ]

Not until all the fish died in the river, _______ how serious the pollution is.[ ]

My pen pal said he would write to me, but I _____ any letters from him so far.