The correct answer is option 3, Nirbhay. Nirbhay is India`s first indigenously designed and developed long-range subsonic cruise missile. This missile can be deployed from multiple platforms, which makes it a versatile weapon for the Indian armed forces.

Option 1, Astra, is incorrect. While Astra is also a missile developed by India, it is an air-to-air missile and not a long-range subsonic cruise missile like Nirbhay.

Option 2, Akash, is also incorrect. Akash is a surface-to-air missile developed by India for air defense purposes. It is not a long-range subsonic cruise missile.

Option 4, Shankhnaad, is a fabricated term. There is no missile named Shankhnaad developed by India, so it is incorrect.

In conclusion, the correct answer is option 3, Nirbhay, as it is India`s first indigenously designed and developed long-range subsonic cruise missile that can be deployed from multiple platforms.