Final answer:
Approximately 10 words should be taught in depth per week in the primary grades. (option B).
Step-by-step explanation:
The average number of words taught in depth per week in the primary grades is approximately 10 words (option B).
According to research, children in the early childhood years experience a rapid increase in their vocabulary. This is known as the "vocabulary spurt," and it involves expanding their vocabulary at a rate of 10-20 new words per week. By the age of 5, children understand about 6,000 words and can speak 2,000 words. They can also define words and question their meanings.
Therefore, teaching around 10 words in depth each week would be an appropriate approach to help primary grade students expand their vocabulary effectively.