question: What are the two types of digestive systems invertebrates may have?
distractor3: gastric and monogastric
distractor1: complete and simple
distractor2: complete and fluid
correct_answer: complete and incomplete
support: Invertebrates have one of two types of digestive system. They are called incomplete and complete digestive systems. Both are shown in Figure below . An incomplete digestive system consists of a digestive cavity with one opening. The single opening serves as both mouth and anus. A complete digestive system consists of a digestive tract with two openings. One opening is the mouth. The other is the anus.