Concept:Discontinuous variation is a type of variation in which individuals fall into separate, distinct categories with no intermediate values.
Explanation:In discontinuous variation, a characteristic has only a few clear-cut phenotypes.
This type of variation is usually controlled by one or a small number of genes.
The ABO blood group system provides a classic example.
A person can only have blood group
A,
B,
AB, or
O.
There is no intermediate blood group between these distinct types.
Because each blood group is a separate category, blood group shows discontinuous variation.
Traits such as head shape, body complexion, and pointed nose show many intermediate forms.
Such traits vary continuously from one extreme to another.
Therefore, among the options given, blood group is the best and correct example of discontinuous variation.
Answer:B. blood group