I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "Almost all species are hermaphrodites, in other words they function as both males and females at the same time – except that in two species of the genus Ocryopsis individuals remain of the same single sex all their lives. The gonads are located in the parts of the internal canal network under the comb rows, and eggs and sperm are released via pores in the epidermis. Fertilization is external in most species, but platyctenids use internal fertilization and keep the eggs in brood chambers until they hatch. Self-fertilization has occasionally been seen in species of the genus Mnemiopsis, and it is thought that most of the hermaphroditic species are self-fertile."? 

what do scientists assume to be true about hermaphroditic animals?