Assertion (A): Arachnoid layer helps in speeding up the transmission of nerve impulses along the axons.

Both A and R are False

Reason — The arachnoid layer is the middle meningeal membrane surrounding the brain and spinal cord; it has no role in increasing the speed of impulse conduction. The structure that actually speeds impulse transmission is the myelin sheath around many axons.
Axon terminals at most synapses release the neurotransmitter acetylcholine not acetylene. Hence the stated Reason is incorrect.