Final answer:
Option 3.
The number of deleterious alleles in a population's gene pool is referred to as genetic load, which indicates the burden on a population's fitness.
Step-by-step explanation:
The number of deleterious alleles present in the gene pool of a population is referred to as genetic load.
It represents the burden of accumulated deleterious mutations in the gene pool and affects the health and fitness of a population.
Genetic drift, on the other hand, is the effect of chance on a population's gene pool and can lead to changes in allelic frequencies due to random sampling.
Genetic variance is the diversity of alleles and genotypes within a population, whereas genetic diversity is a broader term that includes genetic variance along with geographical and other types of variation.
Therefore, the correct option in the final answer is 3) Genetic load.