What are the following is the primary reason that selective breeding cannot completely eliminate genetic diseases or unwanted traits from a population?

Selective breeding cannot completely eliminate genetic diseases or unwanted traits from a population primarily because of genetic variability and the complex nature of inheritance. Many traits are influenced by multiple genes, and some genetic diseases may not manifest until later in life or may be carried by asymptomatic individuals. Additionally, the introduction of new genetic material from outside the population can reintroduce unwanted traits, making it challenging to achieve complete elimination.