Analysis of test questions: The "death of roommate caused by poisoning" in the topic means that the life and health of others have been infringed; "Being sentenced to death and deprived of political rights for life" means that those who violate the law will be prosecuted, which embodies the mandatory nature of the law. Therefore, BCD is correct, and option A confuses the difference between general illegality and crime, which is wrong. The wrong option is a.