If the land area of the earth is about 55,000,000 square miles, the area that can be explored in space is probably______.
A. 55,000,000 square miles
B. 70,000,000 square miles
C. 13,720,000 square miles
D. 550,000,000 square miles
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The writer thinks that modem explorers______.
A. may be lonely
B. can not conquer their fears
C. will keep in touch with the earth
D. can not have connection with the earth
According to the passage, what causes Parkinson's disease？
A. The dopaminergic nerve cells are impaired by the victim cells.
B. The dopaminergic nerve cells can no longer coordinate movement.
C. There are tumors in the brain.
D. There are not enough dopaminergic neurons in the brain.
【C1】
A. and so
B. or so
C. on so
D. so on
【C2】
A. increased
B. got
C. reduced
D. reached
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