Association between Barnacles and Whales/Limulus is
a. Symbiosis
b. Commensalism
c. Parasitism
d. Predatorship

Hint: Some animals live in close association or interaction with other organisms. These interactions are of two types – intraspecific and interspecific. In intra-specific, interaction is found between organisms of the same species, while in inter-specific, interaction is between organisms of different species.

Complete answer:
Interactions between organisms are of many types such as symbiosis, commensalism, parasitism, mutualism, predation, etc.
Commensalism is a type of interaction in which one of the organisms has benefited from the interaction while the other organism is neither benefited or harmed in anyways. In the case of barnacles and whales, barnacles get attached to the whales and are benefitted from them. Barnacles start their life cycle as larvae that get attached to the whales when the whales come near the surface of the ocean to feed.

When barnacles mature, they build their shells on the bodies of the whales and also make cavities on their bodies from where they get their nutrition. As whales move from one place to another in the ocean, barnacles move freely with them. Barnacles are so small in comparison to the whales that even large colonies of barnacles do not affect whales in any form. While in this interaction, whales are neither benefited nor harmed.

Hence, the correct answer is option (B).

Note: Symbiosis is a type of biological interaction found between organisms (symbionts). It can be further divided into mutualism, commensalism, and parasitism. The symbionts can be of the same species or different.
In parasitism, parasites attach to other organisms and get benefitted, while the host is being harmed. Parasites can also live inside the body of the host and are known as endoparasites.
In predation, one organism predates (kills) and feeds on the other organism (prey).