A girl is jumping on a trampoline with her arms in the air , while a boy in a blue shirt is bouncing on his stomach .
Chances are about even that a brother and sister bouncing each other on a trampoline .
Chances are about even that a brother and sister bouncing each other on a trampoline .
There is almost no chance that a brother and sister bouncing each other on a trampoline .
A brother and sister bouncing each other on a trampoline .