The specific defenses of the immune system include a variety of cells that circulate in the blood and that make up organs such as the spleen and thymus. how are the cells of the immune system able to differentiate pathogens from the cells of the body?

a. the cells of pathogens are much smaller than human body cells.
b. pathogens move through the body, while human body cells are stationary.
c. pathogens contain foreign molecules, or antigens, on their outer surface.
d. pathogens release foreign molecules, or antigens, when cells of the immune system approach them.

C. Pathogens contain foreign molecules, or antigens, on their outer surface.

image result for how many calories of energy will 20 grams of carbohydrates provide in one gram provides 4 calories

consuming the right balance of protein, carbohydrates and fat can you maintain a healthy weight and optimize your energy levels. protein and carbohydrates both contain 4 calories per gram, while fat provides 9 calories per gram.

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.