Type the correct answer in each box. Use numerals instead of words. If necessary, use / for the fraction bar. The following chemical equation shows the combustion of ethane. Balance the equation by filling in the coefficients.

C2H6 +
O2 →
CO2 +
H2O

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.