The following are clauses from a contract. Indicate which one of the clauses is an entrenchment clause:

"The purchaser guarantees that the motor vehicle is a $1990$ model."

b$.$ "The lessor shall be entitled to cancel the contract in the event of the lessee's failure to pay the rental due as stipulated in this Agreement"

c$.$ "Should the supplier fail to supply the goods on the dates as indicated in Annexure A$,$ the supplier shall be liable for the payment of $N$$$500\mathrm{.}00($Five Hundred Namibia Dollars$)$ for each day of non$-$delivery"

"The parties hereto consent that there shall be no variation of the terms or conditions of the contract unless such variation is reduced to writing and signed by both parties"

e$.$ None of these answers.