The border between Uganda and the Democratic Republic of Congo was always considered the River Semliki. However, since 1960, the rate of mountain glacier
melt has increased and the river's course has changed many times. Satellite
imagery reveals over 100 changes and widened considerably in that time. In turn,
some towns that were once Ugandan and now Congolese and vice versa. The
changing location only became one of concern and dispute when the area
containing oil was affected by the changing course. *
R- Operational
S- Allocational
M-Definitional
O- Locational

This is an example of an allocational border.

Explanation:

DR Congo and Uganda have a very problematic boundary. The reason for that is that the boundary is decided to be a river, but as we all know rivers are not static and they can change their courses and width over time, and in some cases, those changes can be rapid. The changes in the course and width of River Semliki have been numerous during the past 50 years, so there has constantly been a situation where territories were switching sides of the border.

Initially, neither DR Congo nor Uganda cared about that, as it was a very small population in question and it is an area that was not of interest. This all changed when reserves of oil were discovered in the area. Both nations want the resources for themselves, but the river is still changing courses regulary, so the resources also switch sides of the boundary. By doing so, the countries have developed a very tense relation, and a conflict is not excluded, giving a perfect example of an allocational boundary in action.

it sounds like either a or c