The number of all possible matrices of order $3\times 3$ with each entry 0 to 1 is
(a)27
(b)18
(c)81
(d)512

As order of $3\times 3$ matrix contains 9 elements. Each element can be selected in 2 ways (it can be either 0 or 1).
Hence, all the nine netries can be chosen in $2^9=512$ ways (by the multiplication principle)
Therefore required number of matrices is 512. So, the correct option is (d).