Answer:
c) The swamp tour brochure promised we would see a variety of interesting "critters": great blue herons, pelicans, otters, mink, armadillos, and alligators.
Explanation:
A. The swamp tour brochure promised: (remove :) we would see a variety of interesting "critters" (add comma after critters) great blue herons, pelicans, otters, mink, armadillos, and alligators, (Remove comma and put period)
b. The swamp tour brochure promised we would see a variety of interesting "critters": (add comma after critters) including great blue herons, pelicans, otters, mink, armadillos, and alligators, (Remove comma and put period)
c. The swamp tour brochure promised we would see a variety of interesting "critters": great blue herons, pelicans, otters, mink, armadillos, and alligators.
d. The swamp tour brochure promised we would see a variety of interesting "critters," including: (remove :) great blue herons, pelicans, otters, mink, armadillos, and alligators, (Remove comma and put period)