[A] : In mammals, ends of presynaptic fibres are enlarged to form synaptic Knobs which are separated by a synaptic cleft from postsynaptic neurons. Each synaptic knob contains many mitochondria and small gran- ule-Iike synaptic vesicles filled with minute packets of the chemical that transmits im- pulses to postsynaptic neurons.
[R]: The chemical transmitters are called neurohumors which proportionate to `K^+` in- flux.
A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false