Cutting off joe's head is a sufficient condition for killing him. a. true b. false 2. cutting off joe's head is a necessary condition for killing him. a. true b. false 3. if lacking a feature f is a sufficient condition for having feature g, then lacking feature f is a necessary condition for having feature g. a. true b. false 4. if having feature f is a sufficient condition for having feature g, then having feature g is a necessary condition for having feature f. a. true b. false