Suppose that if the price of plane tickets increased, more people would choose to travel by train. If this happened, you would know that:

A.plane tickets are an inferior good.

B.the cross-price elasticity between plane tickets and train tickets is positive.

C.plane tickets and train tickets are complements.

D.the cross-price elasticity between plane tickets and train tickets is negative.

正确答案：the cross-price elasticity between plane tickets and train tickets is positive.