Question

what should marketing plans include?
actions that need to occur to reach the desired marketing results
new inventory items
customer data and purchase history
people involved in marketing strategies

Explanation:

A marketing plan outlines the actions required to achieve marketing goals. "New inventory items" relate to inventory management (not marketing plan core), "Customer data and purchase history" are for analysis (not plan inclusion), "People involved" is about team (not plan's main inclusion). The first option defines the actionable steps for desired marketing results, which is a key part of a marketing plan.

Answer:

Actions that need to occur to reach the desired marketing results