Exact Match Impression Share metrics:
- are only available at the account level.
- summarize impression share statistics for all keywords currently set to exact match.
- calculate impression share as if all keywords were set to exact match.
- are available for both Search and Display Network campaigns.
Correct Answer is:
Calculate impression share as if all keywords were set to exact match.
Explanation: Exact match impression share is the percentage of impressions that your campaign received for searches that exactly matched your keyword, divided by the estimated number of exact match impressions you were eligible to receive.
You can read more here: https://support.google.com/adwords/answer/2497703?hl=en