Please help again.. i need help on both of those ..

Creation of an unnaturally uniform sample to represent a diverse populationcan be avoided by: a. including only willing b. asking another scientist for .c. choosing only identical participants. d. selecting individuals at random.

Acell in the human nervous system whose primary function is to form myelin and the blood-brain barrier, respond to injury, remove debris, and enhance learning and memory is called a(n) cell.

Which term describes a normal value for something in the body? a. homeostasis b. set point c. feedback loop d. integration center