Question

what is a mono - hybrid cross?
crossing two different traits simultaneously
crossing two individuals with the same trait
crossing two different species

Explanation:

A mono - hybrid cross is a genetic cross that involves the study of a single trait. When two individuals with the same trait (homozygous or heterozygous for that trait) are crossed, it is a mono - hybrid cross. For example, in Mendel's experiments with pea plants, crossing two plants for the trait of flower color (e.g., purple vs. white) where each plant has a particular genotype for that single trait is a mono - hybrid cross.

Answer:

crossing two individuals with the same trait