The Hubble Space Telescope ______ launched in 1990 ______ has revolutionized our understanding of the universe.
Which choice completes the text so that it conforms to the conventions of Standard English?
- A
—,
- Bcheck_circle
, ,
- C
, —
- D
—, —
Explanation
A pair of commas (", ,") properly sets off the nonessential phrase. Mixed dash-comma pairings are nonstandard, and a single dash creates an unbalanced break.