What country was not one of the three that divided poland among themselves?

austria
russia
britain
prussia

In English, the term "Partitions of Poland" is sometimes used geographically as toponymy, to mean the three parts that the partitioning powers divided the Commonwealth into the Austrian Partition, the Prussian Partition and the Russian Partition. In Polish, there are two separate words for the two meanings. The consecutive acts of dividing and annexation of Poland are referred to as rozbiór (plural: rozbiory), while the term zabór (pl. zabory) means each part of the Commonwealth annexed in 1772–95 becoming part of Imperial Russia, Prussia, Austria England would be your answer.