question 22222222222222222

I am having difficulty grasping the rationale behind utilizing variations for A and B, and combinations for C and D. The underlying logic suggests that for A and B, it doesn't matter in which order we place the banners on social media platform 1 and platform 2. On the contrary, for C and D, the question explicitly states, "how many ways we can pick which of the 8 banners to use," implying that the order does matter.

I'm curious why we didn't employ combinations for A and B, where the order doesn't matter, and variations for C and D, where the order is significant. Could you please provide some clarification on this choice of methodology?