Even though the direct costs of malpractice disputes amounts to a sum lower than one percent of the $541 billion the nation spent on health care last year, doctors say fear of lawsuits plays a major role in health-care inflation.

(A) amounts to a sum lower

(B) amounts to less

(C) amounted to less

(D) amounted to lower（C）

(E) amounted to a lower sum

关于last year的修饰问题：even though last year...这样就知道last year 是修饰整个分句，但是放在分句句末我觉得会产生修饰the nation spent on health care 的歧异？ 这样的话，若B项 改成：amout to less.就不知道该选B还是C？

牛牛指教！

对简单句是这样，可是复杂句呢? 也许是我想多了吧