Solution:
The cost of 64-ounce bottle is

The cost of a 120-ounce bottle is

Step 1:
The cost per ounce for the 64-ounce bottle will be calculated below as

Step 2:
The cost per ounce of the 120-ounce bottle will be calculated below as

The difference in the price per ounce is

Hence,
The final answer is
It is a better buy to buy the 120-ounce bottle. You will save 0.01
OPTION D is the right answer