1£®Most of the waste metal can______(put) to use again.

2£®Electricity__________(discover) two thousand years ago.

3£®This part of the seabed__________(explore) many times.

4£®Much useful information about these planets__________(collect) since 1971.

5£®Outer space__________(not explore) by people before 1957.

6£®Much parking space in cities__________(save) by using small cars.

7£®The first railway in the world__________(design) in the last century.

8£®Computer science__________(teach) now almost in all universities and institutes.

9£®Five units of this textbook__________(study) by the end of last month.

10£®In this school English__________(teach) through TV.