Bamboo is ___ grass, but not tree.
A.a type of
B.a pile of
C.a kind of
D.a piece of
答案:C
乒乓球被踩瘪后,放到热水中又会重新鼓起来.其原因是( )
A.球内气体中微粒体积增大
B.球内气体中微粒间空隙增大
C.球内气体中微粒质量增大
D.球内气体中微粒分解成更多微粒
四角花梁头