连词成句。

1. was, while, walking, I, saw, to, I, a, in, bird, school, a, tree

2.  an, this, story, exciting, is

3.  do, sports, you, best, what, like

4.in, he, football, does, playing, well

5. the, morning, I, him, sing, heard, song, this

CI代表（）

A.心指数

B.肺循环

C.每搏指数

D.右心室做功指数