For some birds the sense of smell appears to paly a role in navigation, since pigeons with surgically removed olfactory nerves ( were found to have increased difficulties ) in homing.
A. were found to have increased difficulties
B. have been found to have increased difficulty
C. were found to have increasing difficulty
D. had been found to have increased difficulties
E. have been found to have increasing difficulties
答案是B,我选的A。不明白为什么要用现在完成时,而且感觉困难应该是复数。麻烦老师讲解。
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提问:
请问这题中“explore”的动发者为什么是“Lina”呢?我在读A选项时总觉得选项中explore的动发者是“A group of films” 因为觉得explore前面的主体是“A group of films”, 而 in 1970 和 Lina 都是修饰films的。