(a) $\mathbb R^n$ and the collection of all polynomials in a variable $x$ of degree smaller than $n$;

(b) $\mathbb R^{mn}$ and $M(m,n)$;

(c) $\mathbb R^n$ and the $(\mathbb R^n)^T$ ($\mathbb R^n$ transposed)

I tried looking up the definition of isomorphism, however I could not find the conditions under which pairs of linear space are isomorphic. Thus, I also do not know what properties I should prove. Could someone please help me out?