Magnus and Mandy Are Sorting Pencils for Their Teacher

Magnus and Mandy are sorting pencils for their teacher.Magnus can sort them into two piles,either separating the long and short pencils,or separating the green and yellow pencils.Mandy has decided to put them into four piles,long green pencils,short green pencils,long yellow pencils,and short yellow pencils.Mandy has apparently mastered

A) class inclusion.
B) seriation.
C) conservation.
D) classification.