While studying for a history exam, Michael finds it easier to recall details if he creates a mental picture relating to the information he is reviewing. What memory strategy is he using

Imagery

Explanation: The retention of information over time is referred to as memory. Finding it easy to recall details by  creating a mental picture relating to the information which is being reviewed translates to using the memory strategy known as imagery. It involves taking what is to be learned and then creating meaningful visual, auditory, or proprioceptic images of the information which ultimately activates memory.

your question is incomplete

explanation:

it would be d). more resources must be obtained to attain that combination of goods and services