The tasks are not easy, but they are usually ___ within 20-30minutes.
The fact has worried many scientists ______ the earth is becoming warmer and warmer these years.
.He has ______ little education that he finds it impossible for him to equal ______ important a task.
China is playing an important role in the world. That’s Laura has come to study Chinese.
Astronauts in a spaceship have to _______weightless conditions _______are quite different from ______are on the earth.
— Can you answer my question? --Sorry, I____________ . Would you repeat that question?