The answer in this case is C - TMS (transcranial magnetic stimulation).
TMS is a tool that has been increasingly used in neuroscience because it is one of the rare tools that has direct, causal effects. This is great because it helps scientists observe whether their starting hypothesis can be tested by shutting down or turning up a part of the brain. Compared to fMRI it doesn't provide only a remote view on what is going on, but an actual, causal change that we can observe in behavior :)
