Event A : Order of matrix A is 3 × 5.

Event B : Order of matrix B is 5 × 3.

Event C : Order of matrix C is 3 × 3.

Product of which two matrices gives a square matrix.

1. AB and AC

2. AB and BC

3. BA and BC

4. AB and BA

We know that,

Resultant matrix order = No. of rows in 1st matrix × No. of columns in 2nd matrix.

Resultant matrix (P) on multiplication of AB has order = 3 × 3.

Resultant matrix (Q) on multiplication of BA has order = 5 × 5.

Both P and Q are square matrix of order 3 and 5 respectively.

Hence, Option 4 is the correct option.