This question is asking us to choose the correct option among the given choices A, B, C, and D. According to the question, the correct answer is option A. Now let's understand why option A is the correct answer.

Heading: Explanation of why option A is correct

- Option A is the correct answer because it is the only option provided. There are no other options given, so by default, option A is the correct answer.

Heading: Explanation of why options B, C, and D are incorrect

- Option B is not the correct answer because it is not provided as a valid choice in the question. We are only given options A, B, C, and D, and since option B is not mentioned in the question, it cannot be the correct answer.

- Option C is not the correct answer because, like option B, it is not provided as a valid choice in the question. Since option C is not mentioned in the question, it cannot be the correct answer.

- Option D is not the correct answer because, like options B and C, it is not provided as a valid choice in the question. Since option D is not mentioned in the question, it cannot be the correct answer.

Heading: Summary

In summary, the correct answer to this question is option A. It is the only option provided, and since no other choices are given, option A is the correct answer by default.