Answer: D. Regulate the thalamus
Explanation:
A pathogen is a disease carrying vector that has the ability to spread using a variety of different mechanisms. A pathogen that is a contagion has the ability to spread through touch. An example of such a pathogen would be the one that results in staph infections.
If you talk about the process of fission in the nuclear field then the most used is U-235 because is the easiest to use. Have in mind that the majority of uses of uranium is U-238 but the easiest to be used is U-235