Animals in the same phylum may have different nervous system structures. for example, octopuses have large, complex brains while clams have a simple network. ladder-like ring-like nerve net

Ring-like.

Explanation:

The nervous system of the mollusks consists, basically, of a ring of nerves around the esophagus and a series of nerve cords that follow to the other regions of the body.  The sensory system is very varied and depends on the group. Some have structures, called statocysts, capable of perceiving environmental variations, others have sensory tentacles and eyes.

a researcher conducts an experiment on the secretion of a particular hormone in mice. scientists inject mice with a substance that stimulates the production of the hormone. the scientists then test the levels of hormones produced by the mice. the tool used to measure the hormones consistently detects the levels at 10 points lower than the actual hormone levels in the mice. this tool makes measurements, but the measurements aren't .

explanation:

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