Choose the correct sentence.
a. marsha riding her bike in the park for exercise.
b. marsha be riding her bike in the park for exercise.
c. marsha rides her bike in the park for exercise.
d. marsha ride her bike in the park for exercise.

c. Marsha rides her bike in the park for exercise.

Explanation:

The first option is wrong as the auxiliary verb "is" is missing from it. Again option be is wrong and would have been right if the "be" used was replace with "is".

Option c is correct as the verb "rides" complements the noun Marsha.

The verb ride goes with a plural noun while rides goes with a singular noun. This is the reason option c is right and d is wrong.

d understatement

answer is b,

"the tracer looks harmless in flight, but the pilot’s bitten lips and white knuckles suggest how dangerous it can be."

it was correct.