Frank Tells Grover That He Can Swim in Frank's Lake

Frank tells Grover that he can swim in Frank's lake whenever he wants. With respect to Grover's right to swim in the lake,

A) Frank can withdraw or recall the right at any time.
B) Grover can exercise the right for the duration of his life .
C) Grover can pass title to the right to his heirs.
D) Grover can force his way into Fran's lake whenever he sees fit.