Doctors still know little about how the Listeria bacterium is spread and why the disease it causes, listeriosis, afflicts some people in a contaminated area though it spares many others.
(A)though it spares (B)where it spares (C)despite sparing (D)when sparing (E)while sparing
Doctors still know little about how the Listeria bacterium is spread and why the disease it causes, listeriosis, afflicts some people in a contaminated area though it spares many others.
Doctors still know little about how the Listeria bacterium is spread and why the disease (which)it causes, listeriosis, afflicts some people in a contaminated area though it spares many others.
it 指 Listeria bacterium
the disease = listeriosis
it 指 disease
同一個句子 it 指代不同事物 所以(A)錯
listeriosis 為appositive(同位語) 因為插入句 (which) it causes 之故 所以前後加逗號隔開
A do , while doing 的结构表示同一时间,同一主语发出两个动作。 见 gmatprep 169题97题
97.(29753-!-item-!-188;#058&003991)
Industrialization and modern methods of insect control have improved the standard of living around the globe while at the same time they have introduced some 100,000 dangerous chemical pollutants, having gone virtually unregulated since they were developed more than 50 years ago.
(A) while at the same time they have introduced some 100,000 dangerous chemical pollutants, having
(B) while at the same time introducing some 100,000 dangerous chemical pollutants that have
(C) while they have introduced some 100,000 dangerous chemical pollutants at the same time, which have
(D) but introducing some 100,000 dangerous chemical pollutants at the same time that have (B)
(E) but at the same time introducing some 100,000 dangerous chemical pollutants, having