The correct option is C Acetylcholine
It is not known exactly what causes this process to begin, although people with Alzheimer's disease have been found to have abnormal amounts of protein (amyloid plaques), fibres (tau tangles) and a chemical called acetylcholine in the brain. These reduce the effectiveness of healthy neurons (nerve cells that carry messages to and from the brain), gradually destroying them. Over time, this damage spreads to several areas of the brain, such as the grey matter (responsible for processing thoughts) and the hippocampus (responsible for memory).