101. 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 (D)
(E) amounted to a lower sum
答案没有问题。只是问，OG解释中，
In D, the adjective lower is erroneously used in place of the noun less as object of the preposition to. 是什么意思？谢谢 | 
