下列正确的是（   ）

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．

如果y是z的反比例函数，z是x的反比例函数，那么y是x的（      ）函数．

阅读下面的文言文，回答问题。

    自古书契多编以竹简^①，其用缣^②帛者谓之为纸。缣贵而简重，并不便于人^③。伦乃造意，用树肤^④、麻头及敝布^⑤、渔网以为纸。元兴^⑥元年奏上之。帝善其能．自是莫不从用焉，故天下成称“蔡侯^⑦纸”。

【注释】①自古书契多编以竹简：自古以来都是把字写在或刻在竹片上，再编成册。②缣(jiān)：细的绸绢。③并不便于人：并且不便于人们使用。 ④树肤：树皮。⑤敝布：破布。  ⑥元兴：东汉和帝的年号。  ⑦蔡侯：即蔡伦，曾被封侯。

如图，△ABC的三边分别切⊙O于D，E，F，若∠A=50°，则∠DEF=（    ）