根据短文内容完成下列各题

    Today l would like to tell you about my dream．

    My dream is a simple but great one．It is to be a teacher．①我从小就梦想做一名老师!②First of all，it is a pleasure for me to be with children．They make me feel ③ happy and young．Furthermore，teachers play an important part in the development of children．They teach children and show them how to be good．When children grow up，they use the knowledge that they have learned to develop their motherland and make it beautiful. I think teaching is one of the ④    (value) things in the world．

    That’s all．Thank you !

活的细胞，细胞膜能够让有用的物质进入细胞，把其他物质挡在细胞外，同时，还能把细胞内产生的废物排出体外，而又不让细胞内有用的物质随便流出．请你总结出细胞膜的功能特性是（  ）

古语道：“人要实，火要虚”。此话的意思是说做人要脚踏实地，才能事业有成；可燃物要架空一些，才能燃烧更旺。“火要虚”的含义是（     ）      

胎儿在母体内发育的场所是（    ）

如图，已知：梯形ABCD中，AD∥BC，AB=DC，求证：∠B=∠C．

​