If two variables are varying with respect to another variable t, i.e., if x=f(t) and y=g(t), then by Chain Rule which of the following is correct?

\(\frac{dy}{dx}\)  = \(\frac{dy}{dt}\) / \(\frac{dx}{dt}\) , if dx/dt\(\neq \) 0 \(\frac{dy}{dx}\)  = \(\frac{dy}{dt}\) x \(\frac{dx}{dt}\) , if dx/dt\(\neq \) 0 \(\frac{dy}{dx}\)  = \(\frac{dy}{dt}\) + \(\frac{dx}{dt}\) , if dx/dt\(\neq \) 0 \(\frac{dy}{dx}\)  = \(\frac{dy}{dt}\) - \(\frac{dx}{dt}\) , if dx/dt\(\neq \) 0

\(\frac{dy}{dx}\)  = \(\frac{dy}{dt}\) / \(\frac{dx}{dt}\) , if dx/dt\(\neq \) 0

By definition.