Two atoms are isotopes of the same element. Which of the following should be different for these two atoms?
A. The behavior in a chemical reaction
B. The number of neutrons
C. The type of element
D. The number of protons

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.