Concept: The phrase “running battle” means a continuing or prolonged disagreement, not a physical fight.
Explanation:The word “battle” here is used figuratively, not literally.
A “running battle” is an ongoing dispute that happens repeatedly over a period of time.
In the sentence, the proprietor and his accountant disagree about the financial report.
The word “running” suggests the conflict is continuous or has happened many times.
It does not mean they actually fought physically.
It also does not mean they struggled to complete the report or had difficulty understanding it.
So the most appropriate interpretation is that they have had a series of arguments about the report.
Answer: B. a series of arguments on the report