Sand or gravel that naturally forms near earth's surface is known as
a. pollen.
b. bedrock.
c. ore.
d. aggregate.

Sand or gravel that naturally forms near Earth's surface is known as aggregate. The correct option among all the options given in the question is option "D".The term aggregate is actually used to define those loosely formed or unconsolidated pieces of rock on the surface of the earth. Aggregate is used for the manufacturing of construction materials like mortar, concrete, roofing shingles, grout and asphaltic concrete. In reality, aggregate is classified on the basis of the gradation and size.

It's probably because some types of violets are blue

None of them. they are likely to occur on any plate boundary