Tom runs a small reptile education booth at the weekend market. He keeps notes on 13 snakes: 4 are purple and 5 are happy. From observing their “math tricks,” he knows that
- all of his happy snakes can add,
- none of his purple snakes can subtract, and
- any snake that can't subtract also can't add.
Which of these conclusions must be true?
ABeing purple is a necessary condition for being happy.
BBeing able to subtract is a sufficient condition for being happy.
CBeing able to add is a sufficient condition for being happy.
DNot being purple is a necessary condition for being happy.
ENot being able to subtract is a necessary condition for being happy.