Teenage is an especially important stage for us, ______we are supposed to go all out to improve ourselves because anything can happen.
| A．what | B．where | C．which | D．that |
Low-cost books in paper covers make ______ some of the world’s best literature to readers.
| A．ordinary | B．available | C．comfortable | D．necessary |
He must be helping the old man to water the flowers, ______?
| A．is he | B．isn’t he | C．must he | D．mustn’t he |
—Can I pay the bill by check?
—Sorry, Madam, but it is our managing rule that payment ______ be made in cash.
| A．shall | B．may | C．will | D．can |
The magazine you lent me ______ among the 10 most popular ones in our school.
| A．named | B．belonged | C．listed | D．ranked |
Professor Smith, along with his assistants, ______ on the project day and night to meet the deadline.
| A．work | B．working | C．is working | D．are working |