Answer:
A
Explanation:
This sentence is the only grammatically correct answer. Why? In a direct question, you directly state your question, for example: "How old are you?" When asking an indirect question (which is what this question is) you first start with a phrase such as "Can/could you tell me", then you add the direct question, but phrase the direct question as you would a statement, basically changing the word order: "Could you please tell me how old you are?"
