题型：名词解释 设f（t）=f(x)=-12t+11，(0≤t＜20，t∈N)-t+41，(20≤t\≤40，t∈N)g（t）=-13t+433（0≤t≤40，t∈N*）．求S=f（t）g（t）的最大值． 查看答案
题型：名词解释 The army is a hard place, but Jack is _____ to be a soldier. [ ]A. concernedB. surprised C. determined D. frightened 查看答案