Your Brother Is an Enthusiatic Hiker

Your brother is an enthusiatic hiker. He returns from a walking vacation and tells you that although he had a good time, he ran into a bit of trouble on one of the days he was away because he had got lost in the woods for several hours. Although he took enough food for the day, your brother ran out of water. Luckily, he came across a small stream and was able to fill up his water bottle and to finish his hike without any further problems. Your brother mentions as an aside that he must have eaten something bad while he was away, because he has had pretty bad diarrhea since he got back. He tells you he doesn't feel too bad, but that he has been having what he describes as "explosive diarrhea." He also complains of abdominal pain. You urge him to go to the doctor because you suspect that he may have something more than just food-related diarrhea.
-Giardiasis involves 

A) treatment with mitochondria-targeting medications.
B) aerosol droplet transmission.
C) a Gram-negative causative agent.
D) a protozoan that uses fimbriae for attachment.
E) production of resistant, infectious cysts.