Final answer:
The correct option is C). The group of organisms that are amoeboid and go through a slug stage are Cellular slime molds, specifically known under the genus Dictyostelium, which belongs to the Amoebozoa supergroup.
Step-by-step explanation:
The group of organisms that are amoeboid and exhibit a slug stage are known as Cellular slime molds. These organisms function as independent amoeboid cells when nutrients are abundant but aggregate into a slug mass when depleted. One well-known genus of cellular slime molds is Dictyostelium, which is notable for its ability to alternate between a single-celled amoeboid stage and a multicellular slug state. In terms of phylogeny and taxonomy, these organisms have previously been considered protozoa or fungi due to features like their heterotrophism and production of fruiting bodies and spores, but they are currently classified under the Amoebozoa supergroup within the Protist kingdom.