Since no mammals can breath under water, they cannot be fish. All things that can breath under water are fish. Major Premise b. All fish can breath under water. All things that can breath under water are fish.
Some fish can breath under water.
All things having gills can breath under water. All things that can breath under water have gills. Some things having gills cannot breath under water. The extended argument as a whole is a. invalid because the second step is invalid b. invalid because both steps are invalid c. valid because the first step is valid d. invalid because the first step is invalid e. valid because both steps are valid 36.