单选题 United States health officials are urging people to stop using electronic cigarettes, known as e-cigarettes. The call to action came after such products were linked to health problems. Five deaths have also been reported. E-cigarettes are a popular substitute for smoking products. The electronic devices heat liquid that includes flavoring, nicotine and other chemicals into vapor — very small particles that users breathe in. Nicotine is found in many plants, including tobacco. E-cigarettes or similar devices also can provide THC or other substances to users. THC is the natural chemical present in marijuana plants that gives users the mental state known as a high. E-cigarettes are said to be safer than normal cigarettes because they do not create the cancer-causing byproducts of burning tobacco. Yet health officials say e-cigarette users have reported shortness of breath and other breathing problems, such as coughing and chest pain. Some have been sick to the stomach, felt very tired, suffered weight loss or developed high body temperatures. One report noted that most of the 53 illnesses reported in Illinois and Wisconsin were related to THC vaping products. But nearly 20 percent of the patients inhaled substances like nicotine from e-cigarettes. Most of the reported cases were of young men. The report found that since no single product or substance has been associated with the illness, persons should consider not using e-cigarettes while this investigation is ongoing. Last November, The Centers for Disease Control and Prevention, or CDC, reported that e-cigarette use increased considerably among U.S. middle and high school students during 2017-2018. Among high school students, it found e-cigarette use rose from 220,000 students in 2011 to 3.05 million in 2018. On Monday, the Food and Drug Administration, or FDA gave a warning to JUUL Labs, maker of the best-selling e-cigarettes. The FDA accused the company of illegally marketing its products as being safer than cigarettes without the agency's approval小题:What trend of e-cigarette use was reported by the CDC