The Jugular Veins Are Commonly Used to Establish a Central

The jugular veins are commonly used to establish a central venous line. Why is it sometimes difficult to pass a catheter from the external jugular vein into the right atrium?

A) The catheter tip may catch in the valves.
B) The vein turns at a right angle before it drains into the subclavian vein.
C) The catheter tip may enter the mouth of the anterior division of the retromandibular vein.
D) The vein may be very small in professional singers.
E) The vein is normally constricted as it passes behind the clavicle