The answer is B) three chromosomes in any one set.
In a human diploid somatic cell (2n), there are 22 chromosomes present in two copies and 1 pair of sex chromosomes. This means there are 23 pairs of chromosomes (so choice C. does not indicate a genetic problem). There are in total 46 chromosomes (23 pairs in 2 copies), that differs in lengths (so choice D. does not indicate a genetic problem). Speaking of a pair of sex chromosomes, there could be two X chromosomes in females or one X and one Y chromosome in males (so choice A. does not indicate a genetic problem).
But, having three chromosomes in any one set suggests a presence of trisomy, which is a condition in which an extra copy of some chromosome is present. This results in a genetic disorder.