I was out town at the time, so I don’t know exactly how it ____________________.
| A．has happened | B．happened | C．happens | D．was happening |
---______ the farmers discovered the entrance to the secret cave in the valley?
--- Totally by chance.
| A．When was it that | B．How was it that | C．How it was that | D．When it was that |
One more month, _______ the grapes in the yard will be ripe.
| A．or | B．otherwise | C．but | D．and |
_______these coins are of different shapes, sizes and colors, they all date back to a long, long time ago.
| A．Since | B．Unless | C．Once | D．While |
When _______ about their opinion of the effect of modern equipment on their performance of tasks, many young people gave a positive response.
| A．asked | B．asking | C．being asked | D．to ask |
-----Have you heard the amazing news?
-----But it _______ be true. Anyone with common sense won’t believe it.
| A．mustn’t | B．can’t | C．may not | D．shouldn’t |