In the stretch reflex, a signal from a sensory neuron that detects stretch in a muscle reaches a motor neuron innervating the stretched muscle via

A) excitatory interneurons in the brain.
B) a single excitatory synapse.
C) inhibitory interneurons in the spinal cord.
D) direct sensory-to-motor-neuron synapses as well as excitatory spinal interneurons.