As a Performance Measure for Social Networks, Share of Voice

As a performance measure for social networks, share of voice is

A) the number of comments users are making on a product or a brand.
B) the percentage of comments users are making on the unique videos posted about a product or brand.
C) the brand's percentage of all the online social media chatter related to a product category or topic.
D) the number of users tweeting about a brand or product.
E) the number of users chatting online about a brand or product.