Which is NOT an example of a microbial symbiosis?

Explanation

Bacteria in the colon and protozoans in termites can have mutually beneficial associations, while a tapeworm lives as a parasite in the cow intestine. Bacteria passing through the placenta describes transmission rather than a symbiotic association, so option c is the exception. Students may choose the tapeworm because it is harmful, overlooking that parasitism is also a type of symbiotic interaction.