地球上有许多生命与我们共同生存。科学家曾估计全球的生物物种共有150万。随着科学研究的深入,这个数字已经上升到3000万~5000万。相比而言,人类只是这众多生物物种的一种。这说明
Teenagers shouldn’t be _______ from school although they don’t do well in their studies.
--- Look! Everything here is under construction. --- What’s the pretty small house that _______ for?
In our class there are 46 students, _______ half wear glasses.
Mr. Thomas is ______ a teacher to us. We look on him as our friend.
---Whose case is it? --- I’m not quite sure. But maybe it _______ Mr. White.