If we eat undercooked or raw fish, we may inadvertently consume tapeworms hidden inside the fish. we can get really sick if we have tapeworms living in our intestines. what kind of relationship exists between humans and tapeworms?
a.) commensalism
b.) mutualism
c.) parasitism

Animal bodies (and even plant bodies for that matter) are complex enough that life couldn't exist without enzymes. enzymes are usually large, complex biological catalysts that are expensive to make. enzymes speed up the rate of chemical reactions without being used up during the reaction (they can be reused many times). they are highly specific in the reactions they regulate. knowing what enzymes are and how they function, why does this explain why complex life forms could not exist if there were no enzymes.

According to the big bang theory, after the "bang," the universe remained dark until about  300,000 yearsone billion yearsthree minutesthree billion years  later, when neutral atoms began to form.

The kind of fertilization found in the majority of aquatic animals is (internal or external) fertilization.