Beliving that her grandmother is hearing-impared, Sharon typicallt speaks very slowly and loudly to her. Actually, her grandmother can hear quite well bur she naturally matchers her speaking rythms to Sharon's, which leads Sharon to speak even more slowly and loudly, and the spiral continues. This is an example of:
(a)-Overaccommodation
(b)-Social equilibrium theory
(c)-Patterned response theory
(d)-Divergence