Questions about "onto" and "linear span of column"

Question

If $T : V^6 \rightarrow V^4$ is a linear transformation

And, It can not be one-to-one.

Let $A$ be a matrix representation of $T$

Then

$T$ is onto if and only if columns of $A$ span $V^4$

This is definition.

My question is we know that there are 6 columns.

Out of these 6 columns, as long as 4 are independent, then Is it onto ?

Answer 1

Yes, because if four of them are independent, they will form a basis for $V^4$