At six-thirty, he gave an order to move out, and the column of vehicles left Fort Detrick's main gate and headed south, toward the Potomac River. It consisted of a line of ordinary automobiles—the officers' family cars, with the officers inside wearing civilian clothes, looking like commuters. The line of cars followed behind two unmarked military vehicles. One was a supply van and the other was a snow-white ambulance. It was an unmarked Level 4 biocontainment ambulance. Inside it there were an Army medical-evacuation team and a biocontainment pod known as a bubble stretcher. This was a combat medical stretcher enclosed by a biocontainment bubble made of clear plastic. If someone was bitten by a monkey, he would go into the bubble, and from there he would be transferred to the Slammer. The supply van was a white unmarked refrigerator truck. This was to hold dead monkeys and tubes of blood.

What is the author’s purpose for including this paragraph?

a.to help the reader visualize the thorough precautions that were in place
b.to persuade the reader that safety precautions should always be followed
c.to inform the reader of what could happen if precautions were overlooked
d.to explain in great detail why such precautions were needed for the situation