What's the body's most widespread nonspecific defense against pathogens? a. tears b. mucus c. saliva d. skin

Structures in cells that carry out specific functions.

Which of the following is a macronutrient? carbohydrates lipids amino acids all of the above

Ecologist have observed a sharp increase of sulfur dioxide in the air . what might be a possible consequence of excessive sulfur dioxide in the air ? a. acid rain b. ozone layer depletion c.ozone layer hole d.increase in sea levels