________ a vocation, and you’ll forget unhappy things
| A．Going on | B．To go on |
| C．Go on | D．If you go on |
The United States of America___one of the most developed countries in the world.
| A．is | B．are | C．was | D．were |
The Olympic Games ____ held every ____ years.
| A．is;four | B．are;four | C．is;five | D．are;five |
A chemical works____ built there.
| A．is to being | B．have been | C．were to | D．has been |
Chairman Mao' s works ____ published.
| A．has been | B．have been | C．was | D．is |
The Arabian Nights ____ well known to the English.
| A．is | B．are | C．was | D．were |