回答问题（共3小题；每小题2分，满分6分）
阅读下面短文，根据第53至第55小题的具体要求，简要回答问题。
BEIJING, May 5(Xinhua) —The number of Chinese children infected with hand-foot-mouth disease (HFMD) continues to rise, with reported cases reaching 9,251 by Monday.
The latest HFMD infections occurred in the southwestern Chongqing Municipality which reported 42 sporadic(零星的) cases since Thursday.
"No fatal or critical cases have been reported in Chongqing so far," said Liu Kejia, vice director of Chongqing Health Bureau. "The disease prevention and control center has sampled some cases and no enterovirus 71 has been confirmed."
Beijing has recorded at least 1,482 cases of the disease in all the 18 districts in the city until Monday, of which 818 were
reported in kindergartens. The neighboring Hebei Province reported 206 cases on Monday.
Altogether 25 children have died of the disease. Tests have confirmed 24 of the deaths were triggered by the virus known as enterovirus 71 or EV71.
According to the Guidelines Regarding Prevention and Control of HFMD published on the Ministry of Health website, HFMD can be caused by a host of intestinal(肠的) viruses, but EV71 and the Coxsackievirus (Cox A 16) were the most common.
Anhui Province, in east China, and Guangdong Province, south China were the worst hit areas. Twenty-two of the deaths occurred in Fuyang, a city in northwestern Anhui, and the rest in Guangdong.
Outbreaks have also occurred in Jiangsu, Hunan, Hubei provinces, according to statistics released by local health departments.
In Anhui alone, 622 new cases were reported on Saturday, including 362 in Fuyang, driving up the number of children 
with HFMD to 5,151 in Anhui.
Guangdong registered 925 cases as of Sunday.
Both EV71 and Cox A16 can cause HFMD, which usually starts with a slight fever followed by blisters and ulcers(溃疡) in the mouth and rashes(皮疹) on the hands and feet.
Those sickened by EV71 often show serious symptoms. It can also lead to meningitis, encephalitis, pulmonary edema and paralysis in some children. There is no vaccine.
The Health Ministry issued a circular(通告) late last month requiring better management and surveillance of the disease, as it expects more cases in the next few months.
The ministry asked hospitals for daily reports on the disease, and for local health departments to report emergencies promptly and increase investment in research into the disease.
53. How many deaths occurred in Guangdong Province according to the passage?
54. Which place was seriously infected as it is reported?
55. Why are children so easily infected?
时，电流表的读数分别为
，在这两种情况下两电阻产生的电功率相等。求：电源的电动势E和内电阻r。