In the first sentence, the 'good idea' is mentioned for the first time hence it requires the article 'a' to be put ahead of it, and city centre is a government district and not a proper noun. Also, it is known to the listener because it is a geographical unit of the city, hence 'the' is used. The first statement is correct, and so is the second statement. The phrase 'to save a rupee is to earn a rupee' is more of a saying, which refers to the rupee as any rupee, not just a specific one, hence 'a' is used, making the second statement correct as well. Since both the statements are correct, Option A is the answer and the other options are incorrect for the above mentioned reasons.