As he wiped sweat from his face on a crowded bus, Wang Jun spoke angrily, ' it is simply too hot today. They say it is 35 degrees, but who believes them?' Mr. Wang, a retired worker, was echoing the feelings of thousands of Beijing people as summer entered its hottest stage. Thursday was the hottest day of the year so far, with the temperature officially reported as 36 degrees. But many people believe the government understates the real figure because regulations (条例 ) passed in the 1950s allow workers to stay at home for all or half day if the temperature is higher than 38 degrees. ' It was at least 40 degrees on Thursday, ' said Liang Guojun, a middle school teacher. ' It was unbearable. But the newspaper said only 36 and forecast rain. Of which there was none. In Beijing, visitors to Daguanyuan Park in the southwest of the city said the ground temperature reached 55 degrees on Thursday. The Beijing Evening News reported yesterday that more than 3 , 000 people had been admitted to hospitals suffering from heat stroke (中暑) , while local power companies were struggling to meet the demand for electricity. A heat wave is sweeping much of the mainland, with temperatures in parts of Beijing, Shandong and Hebei provinces reaching as high as 39 degrees. Xinhua said the average temperature in Beijing on Thursday was 36 degrees but in the northern part of Tanghe Kou it was 39 degrees. Hundreds of people suffering fevers were treated at hospitals. The Chaoyang hospital in northeast Beijing reported 55 such cases on Wednesday. They said most were caused by the difference in temperature between air-conditioned areas and outdoors. Mr. Liang said the regulation on stopping work when the temperature reached 38 degrees was passed in the 1950s when Beijing had no air-conditioning and depended on fans—either handheld or electric. 'But in those days the temperature rarely reached 38 degrees, so the rule was not actually used. Now we have had years of global warming and industrial pollution and the summers get hotter each year, which means that the temperature is often higher than 38. But an official from the Beijing Meteorological Observatory (北京气象台) said they had no knowledge of any such regulation. Whom does the underlined word 'they' (Paragraph 1) refer to?