Explanation:

A – IV; B – II; C – I; D – III

A dihybrid cross describes a mating experiment between two organisms that are identically hybrid for two traits. A hybrid organism is one that is heterozygous, which means that is carries two different alleles at a particular genetic position, or locus.

A monohybrid cross is a cross between two organisms with different variations at one genetic locus of interest. The character being studied in a monohybrid cross are governed by two or multiple variations for a single locus. 

Substitution is a type of mutation where one base pair is replaced by a different base pair. The term also refers to the replacement of one amino acid in a protein with a different amino acid.

In particular, multiple allelism is the condition wherein three or more alleles of a gene are present. Thus, the term multiple alleles pertain to the presence of three or more alleles for a particular gene. Multiple allelism is best illustrated by the ABO blood group system in humans