What is the main idea of the passage?
A.There is a new particle called calcium nitrate.
B.Factories are polluting the environment.
C.Climate models have to be updated because of the new particle calcium nitrate.
D.Calcium nitrate lias chemical properties different from other dust particles.

__________(9)
A.for
B.at
C.with
D.against

_________(7)
A.take
B.get
C.have
D.make

Choose the best answer to the following questions.
After Mariana _______ her exam, I _______ her out to eat.
A.was finishing / would take
B.finished / had taken
C.will finish / have taken
D.has finished / will take

Choose the best answer to the following questions.
_______, Joe stays in bed and reads magazines.
A.Whenever raining
B.As it will be raining
C.When it will rain
D.Whenever it rains

Choose the best answer to the following questions.
Jones _______ after everyone _______.
A.speaks / will eat
B.will speak / has eaten
C.is speaking / eats
D.has spoken / will have eaten

Choose the best answer to the following questions.
_______ my homework, I went to bed.
A.After I had finished
B.After finished
C.Finished
D.After had finished

Choose the best answer to the following questions.
We saw many beautiful birds _______ in the lake.
A.when we are fishing
B.while fishing
C.while fished
D.fishing

Choose the best answer to the following questions.
_______, I will give him the report.
A.When he will return
B.When he returns
C.Until he will return
D.No sooner he returns

Choose the best answer to the following questions.
_________ you finish typing that report, make five copies of it and give it to the officers.
A.While
B.When
C.But
D.Although