What is a “metric” in Google Analytics?

• A dimension that can help you analyze site performance.
• The numbers in a data set often paired with dimensions.
• The dates in your date range.
• A segment of data separated out in a report for comparison.

Correct answer is:

• The numbers in a data set often paired with dimensions.

Explanation: Metrics are quantitative measurements. The metric Sessions is the total number of sessions. The metric Pages/Session is the average number of pages viewed per session.

Read more here: https://support.google.com/analytics/answer/1033861