At the beginning of September when the university enrollment came, there were several mobile phone operators who went to a university campus to promote product sales. Several operators launched free package services. However, one of the operators launched a package at a favorable price. Students advertised that what other operators call "free" packages is to obtain operating expenses by selling consumer identity information. Which of the following, if true, would most question the propaganda of the salesperson? ['There is a clear law that mobile phone operators must not sell consumer identity information.', 'It is difficult to guarantee that operators with favorable prices will not sell the identity information of consumers.', 'Poor mobile phone signal provided by free plan operator.', 'Free tier operators obtain operating expenses through advertising.']