问题如下：
An analyst thinks that actual price volatility of A crude oil has been higher than its expected volatility, and he expects this trend to continue. Which position should the analyst take?
选项：
A. a long volatility swap on A crude oil
B. a short volatility swap on A crude oil
C. a short position in an excess return swap that is based on a fixed level of the commodity Index.
解释：
A is correct.
因为预测A原油实际的price volatility是要高于预期的price volatility，当实际波动小于预期波动时，波动互换卖方获利，当实际波动大于预期波动时，波动互换买方获利，所以应该long volatility swap。
