The surety stands discharged

The surety is discharged in the following circumstances:

By Revocation: A surety can revoke the guarantee for future transactions by giving notice to the creditor. However, he remains liable for past transactions.

By Death: Unless there is a contract to the contrary, the death of the surety operates as a revocation of a continuing guarantee in respect of future transactions.

By Variance in Terms: If the terms of the contract between the principal debtor and the creditor are changed without the consent of the surety, then the surety is discharged from liability as he did not agree to the new terms.

Hence, the surety stands discharged in all the scenarios mentioned in options A, B, and C.