Answer:
2 chromosomes
Step-by-step explanation:
The cell of an eukaryotic organism like roundworm contains the Nucleus, which harbors the genetic material embedded in the chromosome. The number of chromosomes of that organism is contained in each cell.
Somatic cells, also called body cells, are all other cells asides sperm and eggs, that form the tissues and organs of an organism. Somatic cells are usually diploid i.e two sets of chromosomes from each parent. In this question, the roundworm has 4 chromosomes in its somatic cell.
The reproductive cells or sex cells (sperm and eggs) of an organism always result from meiotic division of specialized cells.
Since meiosis is a kind of division that results in cells with their chromosome number reduced by half (haploid), it therefore means that the ovum and sperm cell will be expected to contain 2 chromosomes each.
This way, when fertilization occurs (sperm and egg fusion), the resulting zygote, which will eventually develop into an adult organism, will have 4 chromosomes.