It is pretty well understood_______ controls the flow of carbon dioxide in and out the atmosphere today.
| A．what | B．when | C．that | D．how |
Don’t respond to any emails _______ personal information, no matter how official they look.
| A．searching | B．asking | C．requesting | D．questioning |
Three hundred firemen raced to the hotel after a smoke detector ______ the alarm soon after midnight.
| A．set off | B．set out | C．gave away | D．gave off |
--- When shall we go camping again?
--- You _______ the day. Any day is OK with me.
| A．tell | B．call | C．make | D．name |
When I met him the other day, it was the first time we _____ each other since we were at school.
| A．saw | B．had seen | C．were seeing | D．have seen |
He must be getting thin, for his trousers _____ badly like a flag in the wind.
| A．are flowing | B．flow | C．flowed | D．have flowed |