Answer:
Option 3.
Explanation:
Diploid cells have paired sets of chromosome and their chromosome number is represented by 2n. Haploid cells contains single chromosomes and their chromosome number is represented by n.
For example human somatic cells are diploid and contains cells 23 pairs of chromosomes or 46 number of chromosomes. Human gametes (sex cells) are haploid cells and consists of 23 number of chromosomes.
Thus, the correct answer is option 3.