需要找一个vega为负，thta为正的吗？

NO.PZ2016082404000037 问题如下 option portfolio exhibits high unfavorable sensitivity to increases in implied volatility anwhile experiencing significant ily losses with the passage of time. Whistrategy woulthe trar most likely employ to hee the portfolio?   Sell short-teoptions anbuy long-ted options.   Buy short-teoptions ansell long-ted options.   Sell short-teoptions ansell long-ted options.   Buy short-teoptions anbuy long-ted options. ANSWER: A Sua portfolio is short vega (volatility) anshort theta (time). We neeto implement a hee this lta-neutraninvolves buying anselling options with fferent maturities. Long positions in short-teoptions have high negative theta and low positive vegHeing cachieveselling short-term options and buying long-term options. 题目不是太明白，麻烦老师详细讲解下。谢谢！

NO.PZ2016082404000037问题如下 option portfolio exhibits high unfavorable sensitivity to increases in implied volatility anwhile experiencing significant ily losses with the passage of time. Whistrategy woulthe trar most likely employ to hee the portfolio?   Sell short-teoptions anbuy long-ted options.   Buy short-teoptions ansell long-ted options.   Sell short-teoptions ansell long-ted options.   Buy short-teoptions anbuy long-ted options. ANSWER: A Sua portfolio is short vega (volatility) anshort theta (time). We neeto implement a hee this lta-neutraninvolves buying anselling options with fferent maturities. Long positions in short-teoptions have high negative theta and low positive vegHeing cachieveselling short-term options and buying long-term options. 老师我想知道为什么是long vega和theta，组合对这俩敏感，不是应该short这俩嘛，目的是希望这俩等于0

NO.PZ2016082404000037问题如下 option portfolio exhibits high unfavorable sensitivity to increases in implied volatility anwhile experiencing significant ily losses with the passage of time. Whistrategy woulthe trar most likely employ to hee the portfolio?   Sell short-teoptions anbuy long-ted options.   Buy short-teoptions ansell long-ted options.   Sell short-teoptions ansell long-ted options.   Buy short-teoptions anbuy long-ted options. ANSWER: A Sua portfolio is short vega (volatility) anshort theta (time). We neeto implement a hee this lta-neutraninvolves buying anselling options with fferent maturities. Long positions in short-teoptions have high negative theta and low positive vegHeing cachieveselling short-term options and buying long-term options. 题目第一句话“option portfolio exhibits high unfavorable sensitivity to increases in implievolatility anwhile experiencing significant ily losses with the passage of time.”给了两个条件，这个组合是short vega和short theta的组合。关于这一点不是很理解，exhibits high unfavorable sensitivity to increases in implievolatility到底是什么意思呢？为什么是short veg另外答案中有一句话We neeto implement a hee this lta-neutral，为什么还要考虑lta-neutral呢？这题考点不是构建组合用vega和theta to hee吗

NO.PZ2016082404000037 option portfolio exhibits high unfavorable sensitivity to increases in implievolatility anwhile experiencing significant ily losses with the passage of time. Whistrategy woulthe trar most likely employ to hee the portfolio?   Sell short-teoptions anbuy long-teoptions.   Buy short-teoptions ansell long-teoptions.   Sell short-teoptions ansell long-teoptions.   Buy short-teoptions anbuy long-teoptions. ANSWER: A Sua portfolio is short vega (volatility) anshort theta (time). We neeto implement a hee this lta-neutraninvolves buying anselling options with fferent maturities. Long positions in short-teoptions have high negative theta anlow positive vegHeing cachieveselling short-term options anbuying long-term options. 没看明白解题思路