Which story problem can be solved using the number sentence 2 n=18?
A Tom had 18 pencils. He gave n pencils away and had 2 left over. How many pencils did Tom give away?
B Alice bought n books and spent $18. Each book cost $2. How many books did Alice buy?
C Maya had n rocks and 2 baskets. She put 18 rocks in each basket. How many rocks did Maya have?
D Pedro saw 2 kinds of birds. He saw 18 robins and n crows. How many crows did Pedro see?