Concept:A sudden change in a gene or chromosome is called a mutation.
Explanation:Genes and chromosomes carry hereditary information from parents to offspring.
A sudden change may occur in the DNA sequence of a gene or in the structure or number of chromosomes.
Such a change can alter the traits of an organism and can sometimes be passed on to future generations.
This sudden, inheritable change is specifically known as a mutation.
Mutations may be spontaneous or induced by external factors like radiation or chemicals.
They are important because they introduce new variations, which form the raw material for evolution.
Answer:Mutation (Option C)