______ rapidly across the steppes of Central Asia, the Mongol cavalry conquered one of the largest empires in history.
Which choice completes the text so that it conforms to the conventions of Standard English?
- A
Moved
- B
They were moving
- C
It moved
- Dcheck_circle
Moving
Explanation
"Moving" is a participle introducing a participial phrase that modifies "the Mongol cavalry." "It moved" or "They were moving" make the sentence a comma splice; "Moved" creates an unclear modifier.