请教几道语法题

yankljUID: 2158457

In addition to painting highly acclaimed portraits. Many cassatt was () to several major art collectors
A.to advise    B.an adviser     C.advised       D.advising
答案是B    但为什么C不行呢?

The early (periods of aviation) in the U.S was marked by (exhibition flights) made by (individual fliers) or by (teams of performs) at country fairs
答案是A   不明白为什么是A