【简答题】气体交换的场所在 ,它由肺泡上皮和基膜围成。肺泡上皮由 和 细胞共同组成。
【简答题】--“______ he have left yesterday?” --“Yes, he ______ yesterday.” --“No, he ______ yesterday.”A. Must; must have left;
can’t have left B. Can; can have left; can’t have left C. Can; must have left;
can...
【单选题】The police have______that he must have left his apartment yesterday evening.
【单选题】He must have left home yesterday, he?
【单选题】The light in his office is out. He_________ left for home.
【简答题】《小树林中的泉水》的体裁是 ,是 的一个分支,是 的一个变体,兼有 两种特性,通常篇幅 ,形式 ,语言灵动。
【多选题】由于人类活动排放至大气中的污染物会引起臭氧层破坏,引起大气臭氧层破坏的主要污染物是( )。
【单选题】.—Steve come back because the window is open. —Yes.but he _______left it open last night.
【单选题】--- Daniel must have lost his job in that unemployment cr, __________he? --- I don’t think so.Yesterday I saw him working together with his colleagues.