taryscienceandfoodsource（老师您讲得非常好，我已经充分了解到您的国家经济，军事科普与食物来源）”
　　“TeacherI'dliketomakealittlesuggestion,however,nexttimeyouspeakfoodsourceoftrouble,bringussomepracticalcomeandseeitwithmyowneyes,infrontofthestudentsaskedtheoxygen'mafraidIw