Even though the direct costs of malpractice diputes amounts of a sum lower than 1 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.

C. amounted to less

D. amounted to lower

og解释是：The sentence does reqiure a noun (less), not an adjective (lower), as the object of the preposition to.

请问less和lower的区别都是依据这个判断么？在意思上如何区别？

Lower是形容词,是长度,高度的概念.

后面是数字,要求用less修饰。如; 修饰时间，数量和距离等的复数名词前用less.如

less than three weeks, less than four hundred dollars, less than fifty

meters.

By 1977, the USA was importing no less than 45% of its oil.

OG说这里要求noun,但我觉得这里less应该是pronoun.

谢谢LS的解答～

另：longman上对less的解释只有aderb/determiner/preposition, less能用作pronoun么？

我对这题一直有疑问。本人觉得og说less是名词显然是错的。less than 1 percent of结构，less做形容词，percent是名词，less修饰percent。