Stephanie is observing a group of adolescents at the mall and documenting their rate of swearing.The group keeps looking over at Stephanie and pointing at her,and they get louder and more obnoxious the longer she observes them.Which term best describes Stephanie's effect on the group

A)  demand characteristics 
B)  disrupting 
C)  reactivity 
D)  confounding

Reactivity

The propensity of a person to react or respond to environmental stimuli or to changes in their internal state.

Adolescents

Individuals in the transition period from childhood to adulthood, often marked by significant physical, psychological, and social changes.

Observes

To notice or perceive something and register it as being significant, typically by paying close attention or by scrutinizing.