问题如下：
9.Lee’s put-based hedge strategy for Solomon’s ETF position would most likely result in a portfolio gamma that is:
选项：
A. negative.
B. neutral.
C. positive.
解释：
C is correct.
Because the gamma of the stock position is 0 and the put gamma is always non-negative, adding a long position in put options would most likely result in a positive portfolio gamma.
Gamma is the change in delta from a small change in the stock’s value. A stock position always has a delta of +1. Because the delta does not change, gamma equals 0.
The gamma of a call equals the gamma of a similar put, which can be proven using put-call parity.
这里是Long的头寸所以Gamma 是Positive，这样理解对吗？