Select from the following. (a). Heart. (b). lungs. (c). immune. (d). germs. (e). mold. (f). Skin. (g). Liver. (h). Stomach.

Fact 1: Skin is used for breathing air by frogs. Fact 2: An apathetic frog is probably a sick frog. Given the two facts above, what largest organ can cause sickness? ?
Answer:
(f).