What does impression share indicate about a product group?

What does impression share indicate about a product group?

A)It predicts your product group’s future impressions
B)It shows how many impressions your product group has received divided by the estimated number that it was eligible to receive
C)It provides an average benchmark of all similar products from other retailers
D)It shows your product group impressions relative to other product groups in the same campaign

Answer is – It shows how many impressions your product group has received divided by the estimated number that it was eligible to receive