A Couple of Weeks Before Her Sister Graduates,Dorothy Says to Her,"I

A couple of weeks before her sister graduates,Dorothy says to her,"I promise to give you a new mountain bike when you graduate." Her sister graduates and Dorothy takes the bike to her sister,who is thrilled to get the bike.Her sister loves the way it rides,but Dorothy has a change of mind.Dorothy sues to recover the bike from her sister.A court is most likely to rule that:

A) Her sister must give the bike back because a promise to make a gift is not enforceable.
B) The sister must give the bike back because all the requirements of a gift have not been met.
C) The sister must give the bike back if Dorothy has asked for its return within a reasonable time.
D) The sister need not give the bike back because the gift has been completed.
E) The sister need not give the bike back,but must pay Dorothy a reasonable amount if she wants to keep the bike and Dorothy requests this within a reasonable time.