When I came into the classroom, I saw some girls _______ happily.

   A. cry           B. talk       C. to run     D. laughing

When I passed the river, I saw some children ______ on the sand.

A. play B. were playing C.playing D. played

That day I saw some parents____at the back of the classroom,___to the teacher .

选词并用其正确的形式完成句子。每词限填一次。