Which of the following are tiny sacs in the axon terminal that hold chemicals that are released into the synapse?

Answer: Synaptic vesicle

Explanation:

It is also known as the Neurotransmitter vesicle, it can be found inside the axon close to the pre-synaptic membrane, it plays the role of releasing it content into the synaptic cleft, this is achieved only by fusing with the membrane, whenever impulse goes down to the axon of a neuron and gets to the axon terminal, the synaptic vesicle is stimulated.