What distinguishes a monogastric digestive system?

A monogastric digestive system is characterized by having a single stomach. This type of digestive system can be found in animals such as humans, pigs, and dogs. The single stomach allows for a more straightforward digestive process where food is broken down and absorbed efficiently without the need for multiple compartments.

In contrast, animals with multiple stomach compartments, like ruminants (e.g., cows, sheep), have a more complex digestive system that helps them break down fibrous plant material. The presence of multiple compartments allows for fermentation and microbial digestion, which is not a function of a monogastric system.

Regarding the other options, while some monogastric animals might not chew food thoroughly, this is not a definitive characteristic of the system itself. Additionally, monogastric animals do produce digestive enzymes to break down food, but these enzymes may not be considered "complex" in comparison to those found in ruminants, where fermentation plays a significant role in digestion. Thus, the defining feature of a monogastric system is its single stomach structure.