Using two-period binomial model, Jack wants to calculate the terminal value of a put option. If the current price of the underlying asset is $150 and the strike price is $120, the size of an up move is 1.69 and a down move is 0.59. Only when the price is below the strike price can the option has a positive value, otherwise the value will be zero. How many terminal nodes can give back positive return？
A.1
B.2
C.0
老师请问为什么选择A. 1 解析不太明白
