Вставьте сказуемое. if the weather bad, they'll stay at home. a) was b) were c) will be d) is e) are

If the weather  will be bad, they'll stay at home.

После if will нельзя ставить,сразу отпадает.Weather едирсвенное число значит were и are тоже отпадают.Там is вариант D