For displaying unique promotion costs in each promotion category from the PROMOTIONS table:

A. SELECT DISTINCT promo_category, promo_cost FROM promotions ORDER BY 1: This query correctly retrieves unique combinations of promo_category and promo_cost, sorting the results based on the promo_category.

D. SELECT DISTINCT promo_category || ' has ' || promo_cost AS COSTS FROM promotions ORDER BY 1: This query correctly combines the category and cost into a single string for each unique combination, using string concatenation and the DISTINCT keyword to ensure uniqueness, sorting by the concatenated string.

Incorrect options:

B: This does not ensure that the combinations of promo_cost and promo_category are unique because DISTINCT was not specified for both columns together.

C: The syntax is incorrect; DISTINCT cannot be applied to a single column partway through a SELECT clause.

E: This is syntactically incorrect as DISTINCT cannot be used twice in the way shown; it must apply to all columns if used at the beginning of a SELECT statement.