Robert Knows How to Say "Red", but When His Cousin

Multiple Choice

Robert knows how to say "red", but when his cousin asks him to name the colours of the cars that drive past their house, he says red for the red cars, the blue cars, the green cars, and the black cars. Robert's use of this word illustrates

A) fast mapping.
B) telegraphic speech.
C) babbling.
D) overextension.