The two girls are so alike that strangers find ____ difficult to tell one from the other.
| A．it | B．them | C．her | D．that |
As we all know, two thirds of the earth’s surface is water, ___ a lot of fish.
| A．provided | B．providing | C．which provides | D．it provides |
Jack is the ______- child in the family; he wants to have a brother.
| A．one | B．single | C．only | D．separate |
Only in this way, directed by the teacher, ______work out the problem the day before.
| A．had they | B．they could | C．could they | D．did they |
He went swimming on a hot day, ________.
| A．only to be drowned | B．so as to be drowned |
| C．in order to be drowned | D．so that he could be drowned |
The wounded policeman ____though doctors made every effort to save him.
| A．died | B．had died | C．killed | D．has been dead |