Intact skin and mucous membranes: First line of defense. 2. : Second line of defense. 3. : Third line of defense. 4. : Innate defense system. 5. : Adaptive defense system.

Skin and mucous membranes are the First line of defense of the body against disease.

First line of defense means that it is the first part which stops the disease infection and prevent it from infecting the animal body.

Skin also protects the body due to its rigid surface which does not allow pathogens inside the body.

Mucous contains white blood cells which attacks on the disease causing microorganisms and kill them before harming the body.

answer; i believe its echoic memory,it is believed to last three to four seconds; good luck

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.