问题如下：
Initially, Fund ABC held active positions in two realestate stocks—one was overweight by 1 %, and the other was underweight by 1%. Fund ABC traded back to benchmark weights on those two stocks. Then, ABC selected two different stocks that were held at benchmark weights, one automobile stock and one technology stock. ABC over-weighted the automobile stock by 1% and underweighted the technology stock by 1%. What was the effect of ABC’s two trades on its active risk? ABC’s active risk:
选项：
A.decreased.
B.remained unchanged.
C.increased.
解释：
C is correct.
考点：Active Share and Active Risk
解析：主动风险受股票之间相关性的影响。不同行业的两只股票的相关性低于同一行业两只股票的相关性。因此，新头寸（汽车/科技股）的相关性低于初始头寸(房地产/房地产)的相关性。两只股票的相关性较低，两只股票头寸对主动风险的贡献就越大。
我的理解和思路，请老师指点：
1、active risk越大，其实指的就是portfolio和benchmark所包含的股票越不像；
2、correlation指的是portfolio和benchmark两者所包含股票的相关性，而不是portfolio内部各股票的相关性；
3、这个portfolio初始投资的是两只房地产（和benchmark差异大），后来换成automobile和technology（和benchmark一致了），所以初始相关性低、调仓后相关性高，所以调仓后的active risk应该是降低了。
