Question

once a preganglionic axon reaches a trunk ganglion, one of three things can happen to the axon. which of the following is not one of these three things?
the axon can ascend or descend the sympathetic trunk to synapse in another trunk ganglion.
the axon can course back into the spinal cord to synapse with preganglionic neurons in a different spinal segment.
the axon can pass through the trunk ganglion and emerge from the sympathetic trunk without synapsing.
the axon can synapse with a ganglionic neuron in the same trunk ganglion.

Explanation:

To solve this, we recall the fate of preganglionic axons in the sympathetic trunk: 1) ascend/descend to synapse in another trunk ganglion, 2) pass through without synapsing, 3) synapse in the same trunk ganglion. The option "The axon can course back into the spinal cord to synapse with preganglionic neurons in a different spinal segment" is not a valid fate.

Answer:

The option: "The axon can course back into the spinal cord to synapse with preganglionic neurons in a different spinal segment."