Olivia has learned to call a toy truck “tru.” Now whenever she sees any toy with wheels, she calls it “tru.” What is Olivia’s response an example of?

Olivia has learned to call a toy truck “tru.” Now whenever she sees any toy with wheels, she calls it “tru.” What is Olivia’s response an example of?
A) overextension
B) underextension
C) expressive language style
D) referential language style