Correct Answer:
B. Each of them
Work benefiting several tenancies is improvement for: Each of them. This is because an 'improvement' in land law typically refers to any work that enhances the value or utility of the land. If a single piece of work, such as an irrigation channel or a shared access road, provides a tangible benefit to multiple distinct tenancies, then it logically constitutes an improvement for every tenancy that derives that benefit. It is not limited to the largest tenancy, nor is it negated if multiple benefit, and the benefit is not solely tied to who paid first. The core principle is the enhancement of the property's utility for its occupants.