Answer: Option 'A' is correct.
Step-by-step explanation:
Cost of 9 ounces of apples = $1.89
Cost of 1 ounce of apple is given by

Now, if he bought 1 pound of apple,
Cost of 1 pound of apple = $2.49
Cost of 16 ounces = $2.49
(∵ 1 pound = 16 ounces)
Cost of 1 ounce of apple is given by

So, Second option is the least expensive if he bought 1 pound of apple for $2.49
Then, he will save which is given by

Hence, option 'A' is correct.