课后题的走向越来越搞不懂了。。。

为什么A不对?
解答说:Emerging markets equities should be considered a distinct asset class as they differ from other equities in terms of diversification potential, informational efficiency, corporate governance, taxation, and currency convertibility.
但是讲义里asset class的第二个点就是说不能有overlapping啊,emerging market跟global market不是被包含关系吗?