Witch events increased the water content in earth’s atmosphere?

After loss of the hydrogen, helium and other hydrogen-containing gases from early Earth due to the Sun's radiation, primitive Earth was devoid of an atmosphere. The first atmosphere was formed by outgassing of gases trapped in the interior of the early Earth, which still goes on today in volcanoes.

the sphincter muscles at the end of the digestive tract is the anus.

the answer is d.) homologous; have mammary glands