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.