Scientists are convinced ______ the positive effect of laughter ______ physical and mental health.
| A．of；at | B．by；in | C．of；on | D．on；at |
Helen always helps her mother do the housework even though going to school ________ most of her day.
| A．takes up | B．makes up | C．saves up | D．uses up |
Mr. Green stood up in defence of the 16-year-old boy, saying that he was not the one________ .
| A．blamed | B．blaming | C．to blame | D．to be blamed |
It was in the factory ________the TV sets were produced________ we met for the first time.
| A．where, where | B．that, where | C．that, that | D．where, that |
They demanded that the books________ to the school library at once.
| A．return | B．should return | C．be returned | D．would be returned |
I got into trouble again. Only then ________ that I should have followed my parents’ advice.
| A．I realized | B．did I realize | C．realized I | D．had I realized |