声音在15℃的空气中的传播速度是 ____m/s．一个同学向一口枯井的井底大喊一声，约1.5s后听到回声，那么这口井的深度大约是 ____m．
Look! There are some birds _______ in the sky. They are very beautiful.
按拼音写汉字。
jiǎ bǎn
ān xiáng
sǎ luò
____
