Some group (G, o) is known to be abelian. Then, which one of the following is true for G?

The rank of the matrix $$\left[ {\matrix{ 0 & 0 & { - 3} \cr 9 & 3 & 5 \cr 3 & 1 & 1 \cr } } \right]$$ is

The inverse of the matrix $$\left[ {\matrix{ 1 & 0 & 1 \cr { - 1} & 1 & 1 \cr 0 & 1 & 0 \cr } } \right]$$ is

If A and B are real symmetric matrices of size n x n. Then, which one of the following is true?