Final answer:
The substance that is two times more acidic than 2.40 has a pH value of 1.20.
Step-by-step explanation:
The pH scale is a measure of acidity, with lower values indicating more acidity. When we say that a substance is 'two times more acidic,' it means that its pH value is two units lower than another substance. In this case, if the pH of the first substance is 2.40, a substance that is two times more acidic would have a pH of 2.40 - 2 = 0.40. Therefore, the correct answer is A) 1.20.