Consider a blood cell in motion in the middle of the sample with a higher density than the fluid around it. What force (or forces) is responsible for providing the centripetal acceleration on a blood cell

you didn't give any options but heres what i can tell you: an inference is likely to change based on additional observations. the latter is something that you have seen or sensed using your sensory organs while the former is like a conclusion out from what you have observed.

the correct answer is 2 and 4

ok yes, but what is the question? as soon as you ask the actual question i will answer it. : )