Scientists are convinced___the positive effect of laughter___physical and mental health.（）
| A． | of;at | B． | by;in |
| C． | of;on | D． | on;at |
. It’s nothing unusual to experience failure, and ought we to be so discouraged.
| A．in no time | B．by all means | C．by no means | D．in any condition |
Only when _______ according to the directions strictly will the medicine work well.
| A．taking | B．to take | C．taken | D．being taken |
It is not immediately clear__________ the financial crisis will soon be over.
| A．since | B．what | C．when | D．whether |
I’d like my bedroom __________ according to the fashionable style of Europe and America.
| A．designed | B．to be designed | C．to design | D．to have designed |
When asked why he went there, he said he was sent there ________ for a space flight.
| A．being trained | B．training | C．to have trained | D．to be trained |