When turning right at a red light, you must:

Answer: A — Come to a complete stop

Red lights indicate that you must come to a complete stop before proceeding. Option A is correct because it follows the rule of coming to a complete stop. Option B is incorrect because slowing down is not the same as coming to a complete stop. Option C is incorrect because increasing speed is not only unnecessary, but also dangerous when making a turn. Option D is incorrect because while making a complete turn is required, coming to a complete stop is also necessary before completing the turn. Therefore, option A is the safest and correct answer in this scenario.