Scientists say it may be five or six years_______it is possible to test this medicine on human patients.
| A．when | B．after | C．before | D．since |
For her, happiness ________ helping those in trouble.
| A．consists of | B．consists in | C．makes up | D．lie in |
I suggested that he _____ the manager before he decided.
| A．telephoned | B．would telephone | C．telephone | D．had to telephone |
His failure in the experiment suggested that he ________ his teacher’s proper instructions.
| A．should not have followed |
| B．should not follow |
| C．mustn’t have followed |
| D．hadn’t followed |
Professor Hawking stepped into the office I knew that there was no hope.
| A．Unless | B．Now that |
| C．Although | D．The moment |
Usually children are allowed to ___________ when they are six years old.
| A．attend school | B．attend the school | C．join school | D．join the school |