IMO: E
is being threatened, experts say, not only by pollutants such as
- survival is singular and hence "is"
- note only by.....but also by idiom and parallelism maintained by "by"
- oil slicks, trash, are examples of pollutants and hence such as

C is wrong since not only being threatened ... but also by dropped... here parallelism is not maintained between "being threatened' and "dropped..."

Yes, OA: E

anju wrote:IMO: E
is being threatened, experts say, not only by pollutants such as
- survival is singular and hence "is"

How did you interpret that its talking about 'survival' --- i thought it refers to colonies since thats what are threatened ...... not the survival

In other words, who are threatened here ? ------ colonies or survival ?

California4jx wrote:Yes, OA: E

anju wrote:IMO: E
is being threatened, experts say, not only by pollutants such as
- survival is singular and hence "is"

How did you interpret that its talking about 'survival' --- i thought it refers to colonies since thats what are threatened ...... not the survival

In other words, who are threatened here ? ------ colonies or survival ?

survival of coral colonies is threatened. so if you neglect the of part, survival is threatened... read the sentence as:
The survival.... is being threatened

hmm ... thanks.