Identify the action reaction pairs in the following situations:
a. Snowball hits a girl in the back. Snowball pushes girl's back; girl's back pushes on snowball.
b. A baseball player catches a ball. Ball pushes on glove, glove pushes on ball.
c. A man takes a step. Man pushes on the ground; ground pushes on the man.
d. A gust of wind strikes a window. Air hits the window; the window pushes on the air.