Which feature of nuclear fission reactions allows these reactions to take place in a chain reaction?

a) thermal energy is released and heats up the reactants.
b) more smaller atoms form that can undergo fission.
c) a larger atom is formed, which can then be split.
d) neutrons start the reaction and are released during it.

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

Can someone me with questions 12 and 13 plz.

What are the three major branches of natural science? • earth and space science, life science, physical science •earth and space science, physical science, chemistry •physical science, life science, chemistry •life science, chemistry, physics