Guido and Hal want to rescind their contract under which Guido sold Hal a mountain bike for $100. To rescind the contract​ Select one:

a. ​Guido must return the $100 and Hal must return the bike.
b. ​Guido must return the $100 only.
c. ​Hal must return the bike only.
d. ​the parties can keep the "benefits" of their bargain.