Non-students don't have to buy books. When Alice has a headache she is grumpy and silent. Alice is quite cheerful today. When Alice has a headache she is either grumpy or silent. Alice is quite talkative today.
All butterflies are light in weight.
All animals except for walruses are docile. No walruses are light in weight. All Wisconsinites are accustomed to winter. People go south in winter only if they are not accustomed to winter. Your car will last only if you keep up with the maintenance.