Various crosses obtained by using a common tester are called as:

Correct option is D

What is a Test Cross?
A test cross is a genetic tool used to evaluate the genotype of an individual by crossing it with a common "tester" parent.
The tester is usually:
A homozygous recessive line (in classical Mendelian genetics)
Or a standard inbred line (in plant breeding programs)
�� Purpose of Test Crosses in Breeding:
To assess combining ability, especially General Combining Ability (GCA) and Specific Combining Ability (SCA).
Used extensively in line × tester analysis where multiple lines are crossed with a single tester.
Helps breeders identify which lines are good general combiners for traits like yield, disease resistance, etc.
�� Clarification of Other Options:
(a) Single crosses – ❌ A cross between two specific inbred lines (A × B).
(b) Double crosses – ❌ A hybrid made by crossing two single crosses: (A × B) × (C × D).
(c) Three-way crosses – ❌ Cross between a single cross and another inbred: (A × B) × C.
(d) Test crosses – ✅ Crosses made using a common tester, used for evaluating breeding lines.