$49-$ The exchange of something of value $($money$,$ a promise to do something or not to do something$)$ shows the parties intend to be bound by the contract. The "something" that is promised or delivered must be a legal detriment. A legal detriment is giving up a legal or property right. It may be concurrent or promise to perform in the future. Find where this definition belongs to$.$

a$-$ Acceptance

$b-$Offer

c$-$ Agreement

d$-$ Consideration