鸟在天空中飞是用in the sky还是at the sky~

鸟在天空中飞是用in the sky还是at the sky~ “在天空中的云”是of the sky、还是in the sky? at the sky 与in the sky 区别 Look at the blue sky in the fly in sky还是fly in the sky? sky in night 还是sky at night? Look At The Sky 在天空中有成百上千只鸟 用英语填空There are ( )( )birds in the sky on the sky与in the sky up in the sky HopeHope,In the sky. fly in the sky