What part of a mollusk contains the digestive tract, circulatory organs, excretory organs, and reproductive organs?

The part of a mollusk that contains the digestive tract, circulatory organs, excretory organs, and reproductive organs is known as the visceral mass. Here are the steps to understand this:

1. Mollusks are a group of invertebrate animals that include various species such as snails, clams, and squids. They have a specific body structure.

2. The body of a mollusk is generally divided into three main parts: the head-foot, the visceral mass, and the mantle.

3. The head-foot contains the sensory and motor organs. It's usually where the mouth and "foot" for movement are located.

4. The mantle is a protective layer that often secretes a shell. It also forms a cavity that can function in respiration and excretion.

5. The visceral mass is the part of the mollusk that contains the internal organs. This includes the digestive tract, circulatory organs, excretory organs, and reproductive organs.

So, the answer to your question is the visceral mass.