The correct answer is option 3, Akbar. Akbar was a Mughal Emperor who introduced the policy of Sulh-i-kul. This policy, also known as the "Universal Peace", aimed to promote religious tolerance and harmony among different communities.

Option 1, Babar, was the first Mughal Emperor and although he laid the foundations of the Mughal Empire, he did not introduce the policy of Sulh-i-kul.

Option 2, Humayun, was the second Mughal Emperor and he had a turbulent reign marked by conflicts and instability, so it is unlikely that he introduced this policy.

Option 4, Shahjahan, was the fifth Mughal Emperor known for his architectural marvels such as the Taj Mahal. However, he did not introduce the policy of Sulh-i-kul.

It was Akbar who actively worked towards religious harmony by adopting inclusive policies, removing discriminatory practices, and fostering dialogue among different religious leaders. He encouraged interfaith discussions and the incorporation of different religious ideas into his court. It was under his leadership that the concept of Sulh-i-kul became an important part of Mughal policy.