Rob is taller than Edwin, Jurgen is shorter than Rob.
Of only one of the following statements, we now certainly know it is correct:
Edwin is taller than Jurgen
Jurgen is taller than Edwin
It cannot be determined if Jurgen or Edwin is tallest.
Statement C is certainly correct. The only thing that can be stated for sure is that Rob is tallest. If Jurgen and Edwin have different heights, one of the other statements is also correct. But if Jurgen and Edwin have the same height, none of the other two statements is correct