GreatasNewtonwas,manyofhisideas____todayandarebeingmodifiedbytheworkofscientistsofourtime.
C
【句意】尽管牛顿非常伟大，然而他的许多观点当前正受到怀疑，并且当今的许多科学家正在努力对这些观点进行修正。
【难点】challenge意为“挑战，怀疑”，常用作及物动词。本句中牛顿的观点受到挑战为一个当前已经发生的事实，故采用现在完成时的被动语态。
By local doctors and nurses, we hope more people.
All of us know, color-blind people often find it difficult to __ between blue and green.