A:where
B:the place
C:which
D:what
一列火车长360米,每秒钟行15米,全车通过一个山洞需40秒,这个山洞长____ 米.
蝗虫的外骨骼对于蝗虫的陆地生活的作用是( )
learn about, a few, come back, be over, thousands of, look for