When I saw the baby bird--away with its mom A.fly B.flew

选A.我是初中老师,我的学生也老有这样的错误.
see 后只不带to 的不定式和doing 做宾补,没有第三种.看下面：
see sb.do 看到某人常做或做过...
see sb.doing 看到某人经常做...（这个句子常带从句when .如：When I come into the classroom,I saw some students laughing.）