In order to yield a

chromosome condition, only one sperm can fertilize one egg.

(haploid,

diploid)

For the yield of a diploid condition, one egg can be fertilized by only one sperm.

Explanation:

All body cells except germ cells are diploid which means, they have 2 sets of chromosomes while the germ cells are haploid which means, they have one set of chromosomes.

It is in the diploid condition, one sperm with 'n' set of chromosomes and one egg with 'n' set of chromosomes meets the required condition for the progeny to be born.