True regarding surface anatomy of internal jugular vein ?

Ans. is 'b' i.e., Line passing from ear lobule to medial end of clavicle SURFACE MARKINGS OF IMPOANT VESSELS OF NECKSurface anatomy of internal jugular vein:Internal jugular vein is marked by a line joining a point on the neck, medial to the ear lobule to a point at the medial end of the clavicle.Surface anatomy of the external jugular vein:Marked by a line joining a point a little below and behind the angle of the mandible to a point on the clavicle just lateral to the posterior border of the sternocleidonastoid.Common carotid aery:Marked by a line joining a point on the sternovlavicular joint to a point on the anterior border of the sternocleidomastoid at the level of upper border of the thyroid cailage.Internal carotid aery:Marked by a line joining a point on the anterior border of the sternocleidommastoid at the level of upper border of thyroid cailage to a point on the posterior border of the condyle of the mandible.External carotid aery:Marked by a line joining a point on the anterior border of the sternocleidommastoid at the level of upper border of thyroid cailage to a point on the posterior border of the neck of the mandible.