A Farm Dam, Usually Dry During Winter, Has Plenty of Water

Multiple Choice

A farm dam, usually dry during winter, has plenty of water and aquatic pond life during the summer. One summer, Sarah returns to the family farm from university. Observing the pond, she is fascinated by some six-legged organisms that can crawl about on submerged surfaces or, when disturbed, seemingly "jet" through the water. Watching further, she is able to conclude that the "mystery organisms" are ambush predators, and their prey includes everything from insects to small fish and tadpoles.
-If the pond organisms are larvae, rather than adults, Sarah should expect them to have all of the following structures, except ________.

A) antennae
B) an open circulatory system
C) an exoskeleton of chitin
D) sex organs