Dyarchy was introduced in the sub-continent by:

The question addresses a key constitutional reform introduced during the British colonial period in the Indian subcontinent.

• British Government is the correct answer. Dyarchy, a system of double government, was introduced by the British Government in India through the Montagu-Chelmsford Reforms, which culminated in the Government of India Act 1919. This system divided provincial subjects into 'reserved' (controlled by the Governor) and 'transferred' (controlled by Indian ministers).
• Congress was a major political party advocating for self-rule, not the authority that introduced constitutional reforms.
• Kings and the Maratha Empire are irrelevant in the context of 20th-century British colonial administration and constitutional changes.

Dyarchy represented an early, albeit limited, attempt at devolving power to Indian representatives.