The important neurotransmitter released by neurons that allows impulses to pass across a synapse is named which of the following?

1. A neurotransmitter must be a synaptic signalling chemical. 2. Haemoglobin is a blood pigment, so option A is wrong. 3. Insulin is a hormone from the pancreas, not a synaptic transmitter, ruling out option B. 4. The neurotransmitter named in the text is acetylcholine, option C. _Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 15 Nervous System "Neurotransmitters", p.228_