Which of the Following Would Change the Allele Frequencies of a Population

Which of the following would change the allele frequencies of a population?

A) DNA is stable from generation to generation and does not change,so allele frequencies do not change.
B) Tall people in a population preferentially marry other tall people and do not marry people who are short or average height.
C) A population on an island remains isolated and no one leaves or moves onto the island.
D) All of the above would change allele frequencies of a population.