Having concentrated for a long time he ____ his work, made some coffee and talked with his colleagues.
| A．put on | B．put aside | C．put off | D．put back |
Since Tom ______ downloaded a virus into his computer, he can not open the file now.
| A．readily | B．horribly | C．accidentally | D．irregularly |
At minus 130℃, a living cell can be ______ for a thousand years.
| A．spared | B．protected | C．preserved | D．developed |
The traditional view is ______ we sleep because our brain is “programmed” to make us do so.
| A．when | B．why | C．whether | D．that |
______ he referred to in his article was unknown to the general reader.
| A．That | B．What | C．Whether | D．Where |
Small sailboats can easily turn over in the water ______ they are not managed carefully.
| A．though | B．before | C．until | D．if |