The plane x=y=z=3 intersects the cylinder x²+y²=5 in an ellipse. Find parametric equations for the tangent line to this ellipse at the point (1,2,1).
Options:
a) r(t) = [1+t, 2+2t, 1+t]
b) r(t) = [1+t, 2+3t, 1+t]
c) r(t) = [1+2t, 2+t, 1+t]
d) r(t) = [1+t, 2+t, 1+2t]