问题如下图：
选项：
A. 
B. 
C. 
解释：
星星_品职助教 · 2019年10月14日
同学你好，
题干的大意是目前的stock index price（可简单理解为股价）为190$，每过一期，股价只有上涨为原来的1.05倍，或者下跌为原来的0.95倍这两种可能，那么在三期过后，一个执行价格为200的option行权可以赚钱的情况有几种。
其实就是像答案解析一样画出二叉树，然后可以发现三期后有四种价格可能，超过200的就要行权，也就是会有一个positive payoff。计算出每个节点的价格后，发现最后一期四个节点中，只有最上面的一个节点价格超过了200，所以可以行权的节点只有一个。这道题其实学完了衍生品中的call option后来做会更好。
但是从数量这门课的角度来看，其实就是从190出发，简单的乘法运算，第一期变成两个可能价格，第二期有三种可能的价格，第三期有四种可能的价格，只要耐心，各个节点上数值别算错了就好。
考试的时候一般不会让算三期这么繁琐。二期的居多，加油
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