Which of the following best defines natural selection?

In a population of beetles, a gene for green coloration confers a higher survival rate against predators compared to brown coloration. Over several generations, what is the most likely outcome concerning allele frequency?

What is directional selection and how does it affect phenotype distribution in a population?

If a population of birds has individuals that are either small with short beaks or large with long beaks due to different feeding niches, what type of selection might this be, and what could be a long-term evolutionary outcome?

How does heterozygote advantage maintain genetic variation in a population, using the sickle cell trait as an example?