A、A doctor in Qatar. B、Nurse Maitland. C、Dr. Brown. D、Agatha Christie. B

In 1977, a baby girl became seriously ill in Qatar, near Saudi Arabia. Doctors were unable to diagnose the cause of her illness with confidence, so she was flown to London and admitted to Hammersmith Hospital, where specialists help was available. She was then only semi-conscious and on the "Dangerously Ill" list. A team of doctors hurried to examine the baby only to discover that they too, were baffled by the very unusual symptoms. While they were discussing the baby’s ease, a nurse asked to speak to them.
    "Excuse me," said Nurse Marsha Maitland, "but I think the baby is suffering from thallium (铊) poisoning."
    "What makes you think that?" Dr. Brown said. "Thallium poisoning is extremely rare."
    "A few days ago, I was reading a novel called A Pale Horse by Agatha Christie," Nurse Maitland explained. "In this book, somebedy uses thallium poison, and all the symptoms are described. They’re exactly the same as the baby’s."
    "You’re very observant and you may be right," another doctor said. "We’ll carry out some tests and find out whether it’s thallium or not."
    The tests showed that the baby had indeed been poisoned by thallium, a rare metallic substance used in making optical glass. Once they knew the cause of the illness, the doctors were able to give the baby the correct treatment. She soon recovered and was sent back to Qatar.