Answer: STIMULUS DISCRIMINATION
Explanation: STIMULUS DISCRIMINATION is a phenomenon in psychology used to describe a situation where an individual learn to respond to an original stimulus and not to other similar stimuli.
Looking at the question,Meg developed fear for needles and not other sharp objects which shows that Meg was able to differentiate needle from other objects like scissors, nails and knives and therefore only have fear for needles which was what gave her the initial pain and bruises following an injection