$A$ capillary network is a network of what?

The smallest lumen blood vessel in the body is:

The two branches of the iliac artery are:

Tunica externa is composed of

Assertion : When there is a fall in the blood pressure due to loss of blood volume,this is compensated by vasoconstriction of veins.
Reason : Veins hold the extra amount of blood which can be shifted to the arteries as required.

Which vein carries oxygenated blood, unlike all other veins?