Anyone got any idea about the below

Customer wish to change 10,000 of activities to the project scope.
What is the contract clause term?

a) Offer clause

b) Acceptance clause

c)
Consideration clause

d) Change clause

Most of the people will choose d but d is
not a contract clause. =>http://en.wikipedia.org/wiki/United_States_contract_law

>>if one agrees to do something he was not otherwise legally obligated to do, it
may be said that he has given consideration

Which one will be the correct answer? After asking few
person, consideration clause sounds correct as this is the new request and
payment need to be reconsider. But i not quite sure about this.