Which of the following properties is/are certain to have been violated by the system?

Let the two concurrent transactions be $T_1$ and $T_2$.

1. Isolation Violation:

   • Both transactions read the balance of account $A$ concurrently as Rs. 11000 before either transaction committed its update.

   • Both wrote back $11000 - 10000 = 1000$ to $A$, leading to a Lost Update anomaly.

   • Because intermediate/concurrent states interfered with each other, the Isolation property was clearly violated.

2. Consistency Violation:

   • The integrity constraint for a transfer requires that the sum of balances $(A + B)$ remains invariant before and after the transactions.

   • Total deducted from $A$ is Rs. 10000, while total credited to $B$ is Rs. 20000, creating Rs. 10000 out of nowhere.

   • This violates the system's consistency constraints, so the Consistency property was violated.

3. Atomicity and Durability:

   • Atomicity requires that all operations of each individual transaction complete successfully or none do. Here, each individual transaction executed its operations (the overwrite occurred due to lack of concurrency control/isolation, not transaction aborts or partial execution).

   • Durability ensures committed changes survive system crashes, which is not violated here.

Hence, B and C are the properties certain to have been violated.