NO.PZ2019052801000061
问题如下：
If the price of a stock is expected to be volatile in the following months, but whether it will increase or decrease is uncertain, which of the following strategy is most beneficial for investors?
选项：
A.A short position in butterfly spread.
B.Create a neutral calendar spread.
C.A long position in butterfly spread.
D.Create a bullish calendar spread.
解释：
A is correct.
考点：spread strategies
解析：Short butterfly spread在股价接近Xm时面临少量亏损，在股价大幅波动远离Xm时获得收益，A正确。
Long butterfly spread在股价接近Xm时获得收益，在股价大幅波动远离Xm时面临少量亏损，C错误。
Calender spread的期权头寸具有相同的标的物、相同的执行价格，但不同的到期日。与butterfly spread相似，当股票价格接近执行价格，获得收益。
long butterfly spread是CL+CH-2CM和PL+PH-2PM，
short butterfly spread是2CM-CL-CH和2PM-PL-PH吗？课上只讲了第一种情况，但是没有说清楚头寸
