The correct answer is Urdu.
Urdu is a pluricentric language with several standardized varieties, including Standard Urdu and Dakhani Urdu. It is the national language of Pakistan and is also spoken by significant populations in India, Bangladesh, and Afghanistan. Urdu is written in the Perso-Arabic script.
Maithili is an Eastern Indo-Aryan language spoken by about 35 million people in India and Nepal. It is the official language of the Indian state of Bihar and is also spoken in the states of Jharkhand, Uttar Pradesh, and West Bengal. Maithili is written in the Devanagari script.
Bhojpuri is an Eastern Indo-Aryan language spoken by about 45 million people in India and Nepal. It is the official language of the Indian state of Bihar and is also spoken in the states of Jharkhand, Uttar Pradesh, and West Bengal. Bhojpuri is written in the Devanagari script.
Sindhi is an Indo-Aryan language spoken by about 20 million people in Pakistan and India. It is the official language of the Pakistani province of Sindh and is also spoken in the Indian state of Gujarat. Sindhi is written in the Sindhi script.
The Eighth Schedule of the Constitution of India lists 22 scheduled languages, which are the official languages of the Union of India. Urdu is not one of these languages.