It is difficult to ________ what the long-term effects of the accident will be.[ ]

Jack can’tconcentrate on his lessons recently.— Yes, that might____why he did so badly in thelast test.[ ]

ou meet some trouble about how to usethis new kind of machine, you canthe instruction.

There is growing _____ among the public about the safety of school buses after many accidents.

Is the boy your brother — It __________ be. I don’t have brothers or sisters at all.