It is called Fertilization and is the fusion of the male and female gamete
A frog's lungs don't work that well, but since it's skin is so thin, oxygen and carbon dioxide can pass trough it.
A chemical interaction is compelled by electrostatic forces which can occur both in vitro (studies are done outside living organisms), and in vivo (scientists conduct their studies with the use of whole living organisms). In simpler terms a chemical reaction is a change that occurs when two or more substances combine to form a new substance.
B which is after c
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