The correct answer is C. Bribe.
Consideration is something of value that is exchanged between parties to a contract. It must be sufficient to induce the parties to enter into the contract, but it does not need to be equal in value.
Money, property, and jewellery are all valid forms of consideration. However, a bribe is not a valid form of consideration because it is not given voluntarily. A bribe is a payment or gift that is made in order to influence someone to act in a way that is not in their best interests.
For example, if a company pays a government official to award them a contract, this would be considered a bribe. The payment would not be considered valid consideration because it was not given voluntarily. The government official would have been acting in their own best interests by accepting the payment, rather than in the best interests of the public.
In conclusion, the correct answer is C. Bribe. A bribe is not a valid form of consideration because it is not given voluntarily.