Which of the following best describes a parametric equation?

Given x(t) = t - 2 and y(t) = 3t + 1, eliminate the parameter t to find the rectangular equation relating x and y.

Given x(t) = 3cos(t), y(t) = 4sin(t), eliminate t using a Pythagorean identity to obtain a rectangular equation.

Given the parametric equations $x=3t$ and $y=2t+1$, for $-6\le t\le 6$, eliminate the parameter to find an equation relating $x$ and $y$. Then, describe the curve represented by this equation.

For the parametric curve given by $x=2\sin t$, $y=5\cos t$, find $\frac{dy}{dx}$ in terms of $t$ and evaluate it at $t=\pi$.