To answer this question, we need to understand the comparative forms of adjectives.
The correct comparative form of the adjective "bad" is "worse." Therefore, the correct option is D) worse.
Option A) bad - This option is incorrect because it is the base form of the adjective, not the comparative form.
Option B) worser - This option is incorrect because "worser" is not a valid comparative form of the adjective "bad."
Option C) worst - This option is incorrect because "worst" is the superlative form of the adjective, not the comparative form.
Option D) worse - This option is correct because it is the correct comparative form of the adjective "bad."
So, the correct answer is D) worse.