I’m mostly using my intuition here, but based on prior knowledge, (iii) would go with B.
This is because it is commonly known that neurons have long stoma (cell bodies) that help them connect with other neurons, as well as bushy ends, called dendrites, that connects the neurons with others. You can see that clearly in B.
Secondly, ii fits with A. Skin cells are lost constantly, as is well known, and the skin itself is comprised of a multitude of layers of skin cells. This means that skin cells are thin. In the picture A, there are thin structures that seem to be flaking off of a surface.
Thirdly, iv goes with D. The inner walls of intestines are lined with long, thin and microscopic structures called villi, which have the function of increasing surface area for absorption of nutrients. The picture shows, indeed, long, thin structures protruding from somewhere, which is an intestine.
Therefore, through process of elimination, i matches with C. I’m not that well versed with cells from the immune system. I’m guessing they’re white blood cells? I’m not sure.