The lining of the uterus is shed because an ovum has not been fertilized
A : a car driving down a hill
Water can act as either a base or an acid. Water acts as an acid by donating a hydrogen ion when it reacts with a stronger base such as sodium hydroxide. Water may also act as a base when it accepts hydrogen ion when reacting with a strong acid such as hydrochloric acid. This is based on Bronsted concept and definition of a base ( proton acceptor) and acid (proton donor). Such a compound that can act as a base and as an acid is called an amphiprotic molecule.
