Tom was noticed __into that room at that time.a .walk b.walks c.walking d.walked
问题描述：
Tom was noticed __into that room at that time.a .walk b.walks c.walking d.walked
答
C
notice sb doing sth改成被动.
notice sb do sth改成被动为sb be noticed to do sth.（即主动不加to的,改成被动需加to）
另外两个不与考虑.