Name the zero vector for each of these vector spaces. (a) The space of degree three polynomials

Question:

Name the zero vector for each of these vector spaces.
(a) The space of degree three polynomials under the natural operations.
(b) The space of 2×4 matrices.
(c) The space {f: [0,,1] → R | f is continuous}.
(d) The space of real-valued functions of one natural number variable.