When Might a Child Experience a "Vocabulary Growth Spurt

When might a child experience a "vocabulary growth spurt"?

A) Usually when formal education begins
B) When parents begin reading regularly to their child(ren)
C) At the onset of first words, which occurs around 12 months
D) After a few months of growth in vocabulary, around 18 months of age
E) Upon enrollment in nursery school where talk with peers becomes essential.