______ became the official residence of the Commander-in-Chief of the British-Indian Army.

Simla

The correct answer is Option (3) → Simla

It became a practice for Viceroys to move to hill stations during the summer months. In 1864, Viceroy John Lawrence officially moved his council to Simla, setting the seal to the practice of shifting capitals during the hot season.
Simla also became the official residence of the commander-in-chief of the Indian army.