–Where are the students? How could they keep us waiting for so long? –They started an hour ago and they ____ be here in fifteen minutes, I think.
My friend, Tom, may have missed taking the flight to Africa, ______ he can’t arrive for another hour.
The sports meeting, due to ______ this weekend, has been put off due to the rain these days.
Researches are convinced ______ the positive effect of laughter ______ physical and mental health.
The ______ scene where the accident happened made him ______ to death.
It suddenly ______ to the detective that the professor was probably murdered by his own wife .