write all the possible relations from A={1,2} to B={0}

Given, A = {1,2} and B = {0}.

We know that, if A and B be two sets, then a relation R from A to B is a subset of A × B.

Now, A × B = {(1,0), (2,0)}

Again, we know that total number of relations from A to B is 2^mn where m and n are the number of elements of two non-empty finite sets A and B respectively.

Here, m = 2 and n = 1

So, number of relations from A to B = 2^mn = 2^2×1 = 4