Which of the following neurotransmitters is inhibitory?

Identify the labelled parts $A, B$ and $C$ from the given diagram.

$GABA$ (Gamma-aminobutyric acid) is a:

Given below are two statements.
Statement $I$ - In chemical synapse,the rate of transmission of impulse is higher in homeotherms than poikilotherms.
Statement $II$ - In chemical synapse,the synaptic cleft has a width of about $3.8 \ nm$.
In the light of the above statements,select the correct option given below:

Parkinson's disease (characterized by tremors and progressive rigidity of limbs) is caused by degeneration of brain neurons that are involved in movement and control. Identify the neurotransmitter responsible for this.

The neurotransmitter which communicates between two neurons or between a neuron and a muscle is