Which of the following prefixes indicates thick?

The prefix that indicates "thick" is "pachy-." This term derives from the Greek word "pachys," which literally translates to "thick." In medical terminology, it is often used to describe conditions or anatomical structures characterized by an increased thickness. For example, "pachycephaly" refers to an abnormal thickening of the skull.

The other prefixes do not relate to thickness. "Hemi-" generally refers to half, as in "hemiplegia," which means paralysis of one side of the body. "Sym-" means together or with, often used in terms such as "symbiosis," where different organisms live together. Similarly, "pano-" means all or everything, used in words like "panorama," which refers to a comprehensive view. Thus, "pachy-" is distinctly related to the concept of thickness, making it the correct choice.