Botanists have long puzzled over one striking feature of the Venus flytrap ______ its ability to count the number of times an insect touches its trigger hairs.
Which choice completes the text so that it conforms to the conventions of Standard English?
- A
,
- Bcheck_circle
:
- C
; that is
- D
—and that is
Explanation
A colon properly introduces an explanation/elaboration of "feature" after an independent clause. A comma is too weak; "; that is" needs a comma after; "—and that is" is wordy and nonstandard.