问题如下图：
选项：
A. 
B. 
C. 
解释：
老师，真实考试中也会有这道题的难度吗？这道题的计算量而且不小。
NO.PZ2017092702000095 问题如下 A call option on a stoinx is valueusing a three-step binomitree with up move thequals 1.05 ana wn move thequals 0.95. The current level of the inx is $190, anthe option exercise priis $200. If the option value is positive when the stopriexcee the exercise priexpiration an$0 otherwise, the number of terminnos with a positive payoff is: A.one. B.two. C.three. A is correct. Only the top no value of $219.9488 excee $200 题目中哪里确定的是 两层，即 先按照1.05 和0.95 先得到一层，然后再根据当前值 *1.05 得到了第三层的数据，就是怎么看出来第三层是terminal数据。
NO.PZ2017092702000095 问题如下 A call option on a stoinx is valueusing a three-step binomitree with up move thequals 1.05 ana wn move thequals 0.95. The current level of the inx is $190, anthe option exercise priis $200. If the option value is positive when the stopriexcee the exercise priexpiration an$0 otherwise, the number of terminnos with a positive payoff is: A.one. B.two. C.three. A is correct. Only the top no value of $219.9488 excee $200 来到第二次上涨的时候不是已经超过200了吗？这是向positive方向折了两次的意思吧？上课好像没详细讲到这东西怎么玩的，可以介绍一下吗
NO.PZ2017092702000095问题如下A call option on a stoinx is valueusing a three-step binomitree with up move thequals 1.05 ana wn move thequals 0.95. The current level of the inx is $190, anthe option exercise priis $200. If the option value is positive when the stopriexcee the exercise priexpiration an$0 otherwise, the number of terminnos with a positive payoff is:A.one.B.two.C.three.A is correct. Only the top no value of $219.9488 excee $200没有看明白答案中三叉树数字是怎么算出来的
NO.PZ2017092702000095 问题如下 A call option on a stoinx is valueusing a three-step binomitree with up move thequals 1.05 ana wn move thequals 0.95. The current level of the inx is $190, anthe option exercise priis $200. If the option value is positive when the stopriexcee the exercise priexpiration an$0 otherwise, the number of terminnos with a positive payoff is: A.one. B.two. C.three. A is correct. Only the top no value of $219.9488 excee $200 If the option value is positive when the stopriexcee the exercise priexpiration an$0 otherwise。这句话是什么意思，在题中、对解题起到了怎样的作用？
NO.PZ2017092702000095问题如下A call option on a stoinx is valueusing a three-step binomitree with up move thequals 1.05 ana wn move thequals 0.95. The current level of the inx is $190, anthe option exercise priis $200. If the option value is positive when the stopriexcee the exercise priexpiration an$0 otherwise, the number of terminnos with a positive payoff is:A.one.B.two.C.three.A is correct. Only the top no value of $219.9488 excee $200题干里面o otherwise是什么意思
