Which of the following illustrates the principle of induction in invertebrates?

A. In an embryo, the presence of a notochord beneath the ectoderm results in the formation of a neural tube.
B. A neuron synapses with another neuron via a neurotransmitter.
C. Eye muscles constrict in response to light.
D. Secretion of TSH stimulates the secretion of thyroxine.
E. The maternal parent induces spontaneous expression of recessive genes.