D. Checking to see if the brake fluid is contaminated
Step-by-step explanation:
Brake fluid are mostly glycol ether based. The brake fluid is the medium through which the force applied on the pedal is transmitted to the brakes to engage or disengage. The brake fluid is placed in a vessel near the engine. This vessel is not air tight. This leads to the oxidation the fluid also the wear of the components of the braking system causes the contamination. The darkness of the color of the fluid indicates the degree of contamination.
