A cross between AaBB × aaBB yields a genotypic ratio of
(a) 1 AaBB : 1aaBB
(b) 1 AaBB : 3 aaBB
(c) 3 AaBB : 1 aaBB
(d) All AaBb

Hint: The characters in a monohybrid cross are governed by two or multiple variations for a single locus and a test cross of a heterozygous individual is solved using the Punnett square. In this type of cross, each parent is chosen to be homozygous for a given trait.

Complete Step by Step Answer:
The monohybrid cross is a cross between two parents possessing a pair of contrasting characters. If a cross satisfies the conditions for a monohybrid cross, it is usually detected by a characteristic distribution of second-generation offspring that is sometimes called the monohybrid ratio.
Genotypic ratio (${ F }_{ 1 }$ generation) : 1 AaBB : 1aaBB
We have to take parents AaBB and aaBB and cross them to get progeny. A parent with genotype AaBB has two types of gametes; AB and aB and a parent with genotype aaBB has only one type of gamete, which is aB. When a cross happens between these parents, the genotype of offspring will be AaBB and aaBB in the ratio of 1:1. The cross is purely based on the mendelian principle.

Additional Information:
- The basic principles of genetics were proposed by Gregor Mendel. He conducted various hybridization experiments on garden peas for seven years and proposed the laws of inheritance in living organisms.
- Mendelian test cross was a method introduced by Gregor Mendel to determine an unknown genotype; a cross between an organism with a homozygous recessive genotype and an organism with an unknown genotype.
So, the correct answer is 1 AaBB: 1 aaBB.

Note:
- Punnett square is a diagram used to predict the genotypes of a cross.
- Genotype is the genetic make-up of an organism and phenotype is the morphology of an organism.