b
a and d should not be considered bc it is not logically correct. c is eliminated because that may not always be the case. therefore it should be b.
Note that this just produces three parametric equations:



In the

plane, this is just he parametric equation for an ellipse (as a function of u). The z is simply a linear function.
The surface is then an ellipse extruded along the z-axis. We get a elliptic cylinder.
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