It would be unfair to clone any extinct animals they were to live in a zoo.
| A．or | B．if | C．but | D．whether |
Hurry up, ________ you will miss the train. It's leaving in ten minutes.
| A．and | B．so | C．however | D．or |
Not only his parents but also his brother ________ to the Summer Palace. They haven't
been back.
| A．have been | B．have gone | C．has been | D．has gone |
You'd better do it ________ your mother did.
| A．when | B．as | C．like | D．because |
______ they are brothers, they don't look like each other at all.
| A．Because | B． Though | C．When | D． As |
--- When did you know the news?
--- I knew nothing about it _________ my friend told me.
| A．after | B．it | C．because | D．until |