GWD-8-18

Q18: According to a recent study of consumer spending on prescription
medications, increases in the sales of the 50 drugs that were
advertised most heavily accounts for almost half of the $20.8 billion increase in drug spending last year, the remainder of which came from sales of the 9,850 prescription medicines that companies did not advertise or advertised very little.

A.    heavily accounts for almost half of the $20.8
billion increase in drug spending last year, the remainder of which
came

B. heavily were what accounted for almost half of the
$20.8 billion increase in drug spending last year; the remainder of the
increase coming

C. heavily accounted for almost half of the $20.8
billion increase in drug spending last year, the remainder of the
increase coming

D.    heavily, accounting for almost half of the $20.8
billion increase in drug spending last year, while the remainder of the
increase came

E. heavily, which accounted for almost half of the
$20.8 billion increase in drug  spending last year, with the
remainder of it coming

答案是C  請問一下C的後面the remainder of .....那句是獨立主格還是同位語

同位語的話是同哪個字? 謝謝