The correct answer is option 1: Attorney-General of India. The Attorney-General of India is the highest law officer in the country and serves as the legal advisor to the government. They have the privilege of being invited to give their expert opinion on legal matters in the Parliament.

Option 2: Chief Justice of India is the head of the judiciary and while they play a crucial role in the interpretation of laws, they are not specifically invited to give their opinion in the Parliament.

Option 3: Chief Election Commissioner of India is responsible for conducting elections and ensuring their fairness. Their role is primarily focused on the electoral process and they are not commonly invited to give their opinion in the Parliament.

Option 4: Comptroller & Auditor General of India is responsible for auditing the accounts of the government. While their findings may be presented in the Parliament, they are not generally invited to give their opinion on legislative matters.