Which of the following choices is a valid argument? a. cassandra owns a mercedes benz.  rich people drive mercedes benz.  therefore, cassandra must be rich. b. all chevys are trucks.  my car is a chevy. c. either colonel mustard or miss scarlet is the culprit.  colonel mustard is not the culprit, therefore, miss scarlet must be.  d. all good teachers come to class on time.  professor simpson comes to class on time, therefore, he must be a good teacher.