What are the four signs of a chemical reaction

Which supports the idea that birds and butterflies both have wings but they do not have a common ancestor with wings? a. the wings are analogous structures that evolved differently and do not have a similar internal structure. b. the wings are homologous structures that evolved differently and do not have a similar internal structure. c. wings of birds are vestigial structures, but the wing structures of bats are not vestigial. d. wings of bats are vestigial structures, but the wing structures of birds are not vestigial

Which of the dna typing techniques do you think you would choose if you had to analyze a dna sample? why?

Compare the valence electron configuration of the nobles gas elements seen here. what statement is correct?