According to the Outside-in Model, most of Earth's water arrived after the Earth Formed, from meteorites or comets. This water would have mixed with the material in Earth's upper layers and also come to the surface through volcanic action. More supporting evidence comes from NASA's DAWN space craft launched in 2007, which found evidence of water on ceres and vesta, the two largest objects in the main asteroid belt located between Mars and Jupiter.
Its A. Eukaryotic cells are found in multicellular organisms which is why they have membranes unlike the prokaryotic single celled organisms
Langerhans' cells are white blood cells in the immune system that normally play an important role in protecting the body against viruses, bacteria and other invaders. They are found in the skin, lymph nodes, spleen, bone marrow and lungs.
