You Want Exactly Nine Gallons of Water,but You Have Only

Multiple Choice

You want exactly nine gallons of water,but you have only a seven-gallon bucket and a five-gallon bucket.Although you,at first,do not see how these two buckets can help,you realize that you can use them in the following way: fill the seven-gallon bucket,then pour it in the five-gallon bucket,leaving two gallons in the seven-gallon bucket.Pour out the five-gallon,pour the two gallons of water in the five-gallon and refill the seven-gallon bucket and you have a total of nine gallons of water.To solve this problem,you had to use

A) selective comparison.
B) selective attention.
C) selective encoding.
D) selective combination.