Question

Lenny, who is not yet three years old, says to his mother, "cereal in this bowl from here now." it is apparent that lenny has not at this stage of his life mastered the _____ of the english language.

Answer 1

I believe the answer is: syntax
In English language, syntax refers to the words arrangement that make a sentence considered 'well-formed' and could be understood.
For most children, the development of syntax could only appear when they're 5 years old or older.