1.) The skin acts as a physical barrier to infection, and is aided by the presence of: a. Beneficial bacteria

b. Bacteriostatic enzymes

c. both a & b

d. None of above

Which of the following is not a major characteristic used to identify minerals? a. hardness c. density b. magnetism d. luster select the best answer from the choices provided a b c d i know it is not d

Atypical human cell is approximately 12.00 μm in diameter and enclosed by a membrane that is 5.000 nm thick. (a) what is the volume of the cell including the membrane? (b) what is the volume of the cell membrane? (c) what percent of the total volume does its membrane occupy? to simplify the calculations, model the cell as a sphere. enter your answers using four significant figures.

Each pair of clay balls represents two planetesimals. if each planetesimal is composed of the same material and is separated he the same distance, which pair experiences the frayed gravitational attraction?