Which statement best describes mutation–selection balance?

Which statement best describes mutation–selection balance?

• A. It occurs when deleterious alleles are removed by selection at the same rate they are introduced by mutation, yielding a stable frequency
• B. It is when mutation stops and selection eliminates all deleterious alleles
• C. It happens when population size is infinite
• D. It occurs only in recessive alleles with selection against aa

Answer: (A)