句子乐园   

 登山队员常用的能源是氢化钙（CaH₂）固体，它和水反应生成氢氧化钙和氢气（CaH₂ + 2H₂O    Ca(OH)₂ + 2H₂↑），氢气供燃烧之需。现有840g氢化钙固体，与足量水反应可生成氢气多少克？

填空题

如图，将矩形ABCD沿直线AC折叠，点B落在点E处，连接DE，BE，若△ABE为等边三角形，且S_△CDE= $\sqrt{3}$ ，则CD的长为____．

选词填空。

excited, skill, may, they, without, but, include, part

    American teenagers(青少年)enjoy doing part-time jobs．They think it's an important____of growing up．They can learn some important____by doing part-time jobs and they can also make some money in this way．
    American teenagers usually begin to do part-time jobs at the age of 14．On weekdays，they____go to work a few hours a week after school．They usually work for longer at weekends．
    In summer,American teenagers are____if they find part—time jobs at camps or swimming pools．These jobs can bring____much fun．
    Some difficult jobs____teaching， nursing and police work．____these jobs can be helpful for their future．When they grow up，the students with work experience are more likely (可能的)to be successful than those____work experience．