Assertion: Hybrid is formed by a cross between two organisms that are different in one, or more than one traits.
Reason: Mendel crossed two plants differing in one trait to obtain F1 plants which are a monohybrid cross.
A) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
B) Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
C) The assertion is true but Reason is false.
D) Assertion and Reason are false.

Hint: A monohybrid cross is a cross between two organisms with different variations at one genetic locus. The character(s) being studied in a monohybrid cross are governed by two or multiple variations or alleles present for a single locus. Traits are the genetic characteristics of a person. In the case of a monohybrid cross, only one trait is used for the cross.

Complete answer:
The monohybrid cross is used to determine the dominant relationship between two alleles and the cross begins with the parental generation. In this one parent is homozygous for one allele, and the other parent is homozygous for the other allele. The offspring make up the first filial or F1 generation. Every member of the F1 generation is heterozygous. The phenotype of the F1 generation expresses the dominant trait.  For example, tall plant TT is crossed with dwarf plant tt.

In F1 generation T X t will yield a hybrid Tt which is a tall plant as tall is dominant over the dwarf. The hybrid is phenotypically similar to the tall plant but genetically it is different. Crossing two members of the F1 generation produces the second filial or F2 generation. Probability predicts that three-quarters of the F2 generation will have the dominant allele's phenotype. And the remaining quarter of the F2 generation will have the recessive allele's phenotype. 

In F2 generation, the hybrids are crossed Tt X Tt. The gametes are T and t


The phenotypic ratio is 3:1 and the genotypic ratio is 1:2:1
Thus, Hybrid is the offspring of two plants or animals of different species or varieties and the monohybrid cross is a mating between two organisms with different variations at one genetic locus of interest.
So, the correct answer is B. 'Both Assertion and Reason are correct. But Reason is not the correct explanation for Assertion'.

Note: The only difference between D-glucose and D-galactose is in the carbon-4. In the case of D-glucose, the -OH is on the right in Fischer Projection, and in the case of D-galactose, the -OH group is on the left. This is the only difference between D-glucose and D-galactose epimers. They are neither enantiomers nor diastereomers or isomers, they are only epimers.