5. Let $v_1, \dots, v_m$ be vectors in an $n$-dimensional vector space $V$. Select each answer that must always
be true. Explain your reasons.
(a) if $m \le n$, then $v_1, \dots, v_m$ are linearly independent.
(b) if $v_1, \dots, v_m$ span $V$, then $m \ge n$.
(c) if $v_1, \dots, v_m$ are linearly dependent, then $v_1$ must be a linear combination of the other vectors.
(d) if $m = n$ and $v_1, \dots, v_m$ span $V$, then $v_1, \dots, v_m$ are linearly independent.