Answer:
D. developmental milestones
Explanation:
Developmental milestones -
It refers to the physical skills , qualities or behaviors that are observed during the growing years of an infant , is referred to as development milestones .
Developmental milestones is also known as specific normative
There are range for every milestone of the stages of developments , like , crawling , walking , speaking etc .
There is some variable age group , where the child leans various activities .
Hence , from the given statement of the question ,
The correct option is D. developmental milestones .