Combine the following pairs of simple sentences into compound sentences. Use a comma and a logical joining word to connect each pair. David has stopped smoking cigarettes. He is now addicted to chewing tobacco. The record kept skipping. There was a dust on the needle. We turned all the lights off. We locked the office door. I will declare my major now. I may change it later. In warm climate zones, water evaporates rapidly. The concentration of salt is greater. The company’s sales increased last year. Its net profit declined. You’ve got to bear in mind that learning to speak a language is a matter of habit formation. Constant practice is essential.