【单选题】How would the man go to Shanghai?
C.
Either by plane or by train.
【单选题】How much more would the man spend if he buys the tickets on the black market?
【单选题】How much would the man pay for the gift?
【简答题】频率的单位是______,简称赫,符号______.
【单选题】How would the man pay for his purchase?