Define and give examples of a primary pollutant

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

What protects the lining of the stomach from acidic gastric juices?

Q: a: in sexually reproducing animals, once fertilization of the egg takes place, the exists as a single cell until cell division begins