John's Son Was Not His Agent but Contracted to Purchase

John's son was not his agent but contracted to purchase a computer in the name of John.When John learned of this,John sternly rebuked his son but continued to use the computer for several weeks.After losing interest in the computer,John offered to return it,saying that the purchase was unauthorized.John:

A) is not liable on the purchase.
B) expressly ratified the purchase.
C) is liable because all children have the apparent authority to contract for their parents.
D) ratified the purchase by John's conduct.