From the passage, we get to know that astronauts are at greater risk of radiation damage
A. if they have less iron concentration.
B. if they have more folate supplements.
C. if they have no gene variations.
D. if they have flown further into the space.
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Which statement is CORRECT about the authors surfing learning experience？
A. He took surfing courses to make peace with coastguards.
B. He has learned surfing for ten years since a motor accident.
C. He was the first person to surf on the steep waves of Cribbar.
D. He could finally heave the sail upright quickly in his own way.
From the passage, we have the impression that the author is
A. tenacious.
B. faithful.
C. pretentious.
D. contemptuous.
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