Explanation:

- Subsidiary Alliance with Avadh: Lord Wellesley, as part of his expansionist policy in India, compelled the Nawab of Avadh to accept the Subsidiary Alliance. This meant that the Nawab had to disband his army and allow British forces to be stationed in his territory.

- Occupation of Rohilkhand: As part of the treaty, the area of Rohilkhand was ceded to the British East India Company. This was a strategic gain for the British as it extended their influence in the north.

- Year of these events: The occupation of Rohilkhand and the enforcement of the Subsidiary Alliance with Avadh occurred in the year 1801.

- Correct Answer: Option 3 - 1801 A.D.