Btatit square dance

The basic properties of a square matrix are:

Matrix AB≠BA, so option (a) is wrong.

| ab | = | a ||| b | = | ba |, so option (b) is correct.

(AB)T=BTAT, so option (c) is wrong.

(AB)2=ABAB≠A2B2, so option (d) is wrong.

So, choose: B.