There is a following sample UI control question but it makes no sense to me:

A customer views a product available in multiple color options. The customer must select only one color for each product.

Which UI control allows a developer to present the user with all color choices at once, without prompting or clicking, while ensuring that the user can only select one of the color options?

a) Radio buttons; b) Text input; c) Drop-down; d) Check box

The answer is obviously a radio button (without prompting or clicking an the user can select only one color. However, there are multiple colors and as per Pega best practices we can't use radio buttons for more than 3 options.

Please clarify. Many people I talked to believe the right answer is drop-down because it also fits the description (allowing to choose 1 color of multiple options). Thank you!