Sand is loose fragments of rock and minerals, with principal its

A B C

component being quartz.

D

Principal its should be its principal, as the possessive pronoun should precede the noun. The correct sentence should read: "Sand is loose fragments of rock and minerals, with its principal component being quartz."

原题及解答如上，但(B)rock是可数名词，不需表达单复数吗?

C的错误很明显。

B要理解为岩石，不可数，但是我还是觉得应该加the.