人造石和陶瓷的区别:why do birds fly south?

why do birds fly south? 脑筋急转弯 Why do birds fly south? riddle:why do birds fly south for winter Can birds fly? ----- Yes,() can why does the bird fly -Why are the birds flying near the ground? 脑筋急转弯 Why does time fly? why do you do that?同义句 Some birds…. very fast in the sky when we were in the park (fly) Birds fly ___for hundreds of miles___they reach the warm lands of Africa.