请教大家prep语法，迷茫呢

139.   (32103-!-item-!-188;#058&006640)

Taste buds are onion-shaped structures with between 50 and 100 taste cells, each of them has fingerlike projections poking through the opening located at the top of the taste bud called the taste pore.

(A) them has fingerlike projections poking through the opening located at the top of the taste bud called the taste pore

(B) them that have fingerlike projections that poke through an opening located at the top of the taste bud, which they call the taste pore

(C) which has fingerlike projections poking through the opening, called the taste pore, located at the top of the taste bud

(D) which having fingerlike projections that poke through an opening, which is called the taste pore, located at the top of the taste bud

(E) which have fingerlike projections that are poking through an opening located at the top of the taste bud called the taste pore

这题为什么不选A，要选C啊，