Question

under the microscope, a blood vessel is observed to have a relatively thin wall, a large lumen, is collapsed, and contains a thick tunica externa. this is probably a(n)
multiple choice
artery.
vein.
capillary.

Explanation:

Veins have relatively thin walls compared to arteries, large lumens, tend to collapse when not filled with blood, and have a thick tunica externa. Arteries have thicker walls to withstand high - pressure blood flow, and capillaries are extremely small with very thin walls for gas and nutrient exchange.

Answer:

B. vein