Coral reefs face many threats from human activity ______ rising ocean temperatures may be the most devastating of all.
Which choice completes the text so that it conforms to the conventions of Standard English?
- A
, that is
- B
:
- C
however
- Dcheck_circle
;
Explanation
Both clauses are independent and contrast in a related way; a semicolon is the cleanest fit. A colon would imply the second explains/defines the first, which it does not. " however" creates a run-on; ", that is" implies restatement.