Eyebrow Hairs Are Always Shorter Than Hairs on Your Head

Eyebrow hairs are always shorter than hairs on your head because _ .

A) they grow much slower
B) the vascular supply of the eyebrow follicle is one- tenth that of the head hair follicle
C) hormones in the eyebrow follicle switch the growth off after it has reached a predetermined length
D) eyebrow follicles are only active for a few months