Final answer:
The measure of the percentage of the target market that has been exposed to a promotional message at least once during a specific time period is referred to as frequency.
Step-by-step explanation:
The measure of the percentage of the target market that has been exposed to a promotional message at least once during a specific time period is referred to as A. frequency. It represents how many times the target market has been exposed to the message, regardless of the number of individuals.
For example, if a promotional message reaches 50% of the target market at least once, the frequency is 1. If it reaches 40% of the target market twice, the frequency is 2.
This measure is important for marketers because it helps them understand how widely their message has been spread and how many opportunities they have had to increase awareness and generate interest.