✅ Correct Answer: A. How long the price of the child product is changed by the promotion
When you assign a Time Plan to a child product within a promotion, the Time Plan defines the duration for which that child product's pricing adjustment or override is valid.
So, for example:
If a promotion includes a discounted setup fee for 3 months only, the Time Plan ensures that the discount only applies during that period.
After the time plan ends, the pricing reverts to the standard pricing.

❌ Why the other options are incorrect:
B. When the entire promotion expires
→ The promotion’s time policy controls when the promotion starts and ends — not the time plan of an individual child product.
C. Which customers are eligible for the child product
→ That’s controlled by context rules, not the time plan.
D. When the time plan begins for the child product
→ The time plan includes both start and duration, but the primary effect is how long the promotional pricing is active — not just the start date.