The gravity of the sun and the moon together cause an ocean motion called

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.

Select the word from the list that best fits the definition the temperature to which air must cool to be saturated

Someone with these questions! pls 30 pts