What type of defense mechanisms does our body have to fight off affections?

The immune system uses white blood cells and antibodies to identify and eliminate organisms that get through the body's natural barriers.

Explanation:

When the immune system is weakened by the virus, the body is especially susceptible to infections by what are usually harmless pathogens because of the reduction of a specific group of T cells. Due to the lack of T cells, the immune system has difficulties properly coordinating the fight against the pathogens in the tissue. This is when white blood cells and antibodies begin their attack. Then the immune system can fight against the infection on all fronts.

White Blood Cell- a colorless cell that circulates in the blood and body fluids and is involved in counteracting foreign substances and disease; a white (blood) cell. There are several types, all amoebic cells with a nucleus, including lymphocytes, granulates, monocles, and macrophages.

Antibodies- a blood protein produced in response to and counteracting a specific antigen. Antibodies combine chemically with substances which the body recognizes as alien, such as bacteria, viruses, and foreign substances in the blood.

the answer is d   for sure : )

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.