Final answer:
Lord Durham recommended the merger of Upper and Lower Canada and the establishment of a responsible government as part of his report following the 1837-1838 rebellions.
Step-by-step explanation:
The person who recommended that Upper and Lower Canada be merged and given a responsible government was Lord Durham. This recommendation was part of the reforms suggested in Lord Durham's Report on the affairs of British North America following the rebellions of 1837-1838.
The report advocated for the union of the two Canadas to ensure a single government and legislative assembly. In doing so, it laid the groundwork for establishing a responsible government where the executive branch would be accountable to an elected legislative assembly rather than to a distant monarch or colonial governor.