Graph the following subsets of R3 and use this to explain which are subspaces: (a) The line

Question:

Graph the following subsets of R3 and use this to explain which are subspaces:
(a) The line (t. -3t)T for t ∈ R.
(b) The helix (cost, sin t, t)T.
(c) The surface x - 2y + 3z = 0.
(d) The unit ball x2 + y2 + z2 < 1.
(e) The cylinder (y + 2)2 -f (z - 1 )2 = 5.
(f) The intersection of the cylinders
(x - l)2 +y2 = 1 and (x + l)2 +y2 = 1.