How many chromatids does a diploid body cell contain just prior to cell division

Just prior to cell division, a diploid body cell (somatic cell) contains twice the number of chromatids as the haploid number, because each chromosome is duplicated during the S phase of the cell cycle. 

For a diploid organism, such as humans, the haploid number (n) of chromosomes is 23. Therefore, just before cell division, a diploid body cell would contain 46 chromatids, as there are 23 pairs of chromosomes, and each chromosome is composed of two sister chromatids following replication.