Equation $\frac{1}{y'}+\frac{1}{y}=\frac{1}{t}$ is linear and separable linear but not separable separable but not linear None of the above
The answer is D. One more? Solution $\frac{1}{y'}=\frac{1}{t}-\frac{1}{y}=\frac{y-t}{yt}$. So $y'=\frac{ty}{y-t}$ seems to me to be neither linear nor separable. (Unless we do weird substitution tricks.)