Explanation:

- 1. AB = BA:

- For matrices, $AB$ always equals $BA$ if matrix $B$ is $A$'s adjugate.

- This is because both $AB$ and $BA$ result in a scalar multiple of the identity matrix.

- This statement is correct.

- 2. AB is a scalar matrix:

- Given $B$ is the adjugate of $A$, $AB$ equals $det(A)\times I$, where $I$ is the identity matrix.

- Hence, $AB$ is indeed a scalar matrix.

- This statement is correct.

- 3. AB can be a null matrix:

- Since $A$ is non-singular, $det(A)\ne 0$.

- Therefore, $AB$ can never be a null matrix.

- This statement is incorrect.

- Therefore, the correct option is Option: 2 - 1 and 2 only.

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