A primary grade mathematics teacher develops the concept of number And numbers sense with help of sets of familiar objects such as 2 pens, 3 fruit, 5 boys, 7 girls etc. by introducing the number as a description of a set of objects the teacher has focused on

Correct option is B

The teacher, by introducing numbers as a description of a set of objects (such as 2 pens, 3 fruit, 5 boys, 7 girls), is focusing on the Cardinal aspects of number.
The cardinal aspect of numbers refers to the concept of counting and the quantity or size of a set, which is what is being emphasized in this context.