Complete the passage with the correct form or tense of the words in brackets.

Television first (1) (appear) some fifty years ago in the 1950s. Since then, it has (2) (be) one of the most popular sources of (3) (entertain) for both the old and the young. Television can (4) (actual) satisfy almost all kinds of taste.It offers cartoons for children, world news, music and many other programs. Ifsomeone is (5) (interest) in sports, for example, he can tune in to a sports channel. There he can enjoy a live broadcast of an (6) (nation) football match. Television is also a very (7) (use) way for companies to advertise their products.

It’s not too hard for us (8) (see) why there is a TV set in almost every home today. And, engineers are developing (9) (interact) TV which allows (10) (communicate)between viewers and producers.

The rockets are a purely measure against nuclear attack. (defense)