参考答案:

1.It is all very well for such things to occur in fiction.
2.Though it may be possible to measure the value of material goods in terms of money,it is extermely difficult to estimate the true value of the services which people perform for us.
3.Radio and television have made it possible for advertisers to capture the attention of millions of people in this way.
4.I bound the base of the tree with sticky tape,making it impossible for the ants to reach the aphids.
5.Perhaps it is the desire for solitude or the chance of making an unexpected discovery that lures people down to the depths of the earth.