单选题 .    Unlike Britain, the U.S. does not have a national health care service. The government does help pay for some medical care for people who are on low incomes and for old people, but most people buy insurance (保险) to help pay for medical care. The problems of those who cannot afford insurance are an important political subject.
    In Britain, when people are ill, they usually go to a family doctor first. However, people in America sometimes go straight to an expert without seeing their family doctor first. Children are usually taken to a doctor who is an expert in the treatment (治疗) of children. In Britain, if a patient needs to see a specialist doctor, their family doctor will usually recommend a specialist.
    Doctors do not go to people's homes when they are ill. People always make appointments to see the doctor in the doctor's office. In a serious situation, people call for an ambulance (救护车). In America, hospitals must treat all seriously ill patients, even if they do not have medical insurance. The government will then help to pay for some of the cost of the medical care.1.  Some medical care is paid by the U.S. government for ______.