· The sentence talks about the extent of the increase in pollution levels. The correct word should emphasize intensity or magnitude.
· "Highly" fits best as it means to a great degree or extent.
Why the other options are incorrect:
· Slowly: Refers to speed, not magnitude, and is irrelevant in this context.
· Primarily: Refers to the main reason or cause, which is unrelated to the extent of increase.
· Chiefly: Synonymous with "primarily," focuses on cause or importance rather than degree.
Thus, the corrected sentence is: "Pollution levels have increased so highly that they are almost killing us."
Hence, option (a) is the answer.
Study Notes
Category
