A feather falls slower than a stone only because the air holds the feather back more than it the stone.
A. does
B. holds
C. will
D. is
网友回答
(答案→)A. does
B. holds
C. will
D. is
解析：英语在使用时尽量避免重复。在进行对比、比较或说明两组事物相同时，用do来代替前面的动词（词组）。空前的it 指代the air, 空上应为holds back, 但为了避免重复，用do 的单三形式does替代上文所用的动词短语。