单项选择题
The Mars turned out to be large patches of __________ land and there is no sign of life there.
单项选择题 Many young Americans have traveled abroad and gotten hooked on __________ foods.
单项选择题 In the quest to find a __________ for cancer, scientists must draw on a collective information base.
单项选择题 He __________ his repeated failures to the bad luck and unfavorable financial conditions.
