Final answer:
Rocky Mountain Spotted Fever is caused by Rickettsia rickettsii and transmitted by hard-bodied ticks like the American dog tick, Rocky Mountain wood tick, and brown dog tick.
Step-by-step explanation:
The diagnostic term Rocky Mountain Spotted Fever (RMSF) is caused by the bacterium Rickettsia rickettsii, an obligate intracellular parasite. This disease is transmitted through the bite of certain hard-bodied ticks.
Specifically, the ticks that can carry this organism are the American dog tick (Dermacentor variabilis), the Rocky Mountain wood tick (D. andersoni), and the brown dog tick (Rhipicephalus sanguineus). Hence, the correct answer to the question is option a) Tick.