Muslim League was established in 1906 at :

Bombay
Lahore
Dhaka
Delhi

The correct answer is (b). The All-India Muslim League was established in 1906 at Dacca (now Dhaka), in British India. It was founded by Nawab Salimullah Khan, the Nawab of Dacca, and other Muslim leaders. The League was formed to protect the rights of Muslims in British India. It played a major role in the Indian independence movement and the partition of India in 1947.

The other options are incorrect. Bombay (now Mumbai) is a city in India. Lahore is a city in Pakistan. Delhi is the capital of India.