We can never expect ____ bluer sky unless we create _____less polluted world.
| A．a; a | B．a; the | C．the; a | D．the; the |
We were all __________ to learn that the hero was a child of only six years old.
| A．tired | B．concerned | C．determined | D．amazed |
English is a language shared by several diverse cultures, each of __________ uses it somewhat differently.
| A．which | B．what | C．them | D．those |
Many young people in the West are expected to leave __________ could be life's most important decision—marriage—almost entirely up to luck.
| A．as | B．that | C．which | D．what |
My chest __________ when I make a deep breath, doctor.
| A．harms | B．wounds | C．hurts | D．injures |
The plane, __________ by another plane, broke into pieces.
| A．crashed | B．to crash |
| C．to be crashing | D．have crashed |