Definition: In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.
Input: Question: What country was Metzger born in? Passage:Metzger was born to a Jewish family in Mainz on March 23, 1932, to a hardware store owner and a homemaker. Some of his relatives perished in the Holocaust. At the suggestion of his sisters, Metzger's father moved to the United States in 1937, followed by his wife and sons in January 1938. Henry Metzger attended the Bronx High School of Science, as did his brother, then earned a bachelor's degree from the University of Rochester in 1953, followed by a medical degree at the Columbia University College of Physicians and Surgeons in 1957. Metzger completed his residency at Columbia Presbyterian Hospital, and joined the Public Health Service in 1959, through which he began working at the National Institutes of Health. After two years of post-doctoral study with Seymour Jonathan Singer, funded partly by the Helen Hay Whitney Fellowship, Metzger returned to the National Institutes of Health, working primarily in the National Institute of Arthritis and Musculoskeletal and Skin Diseases.
 Links: a. Mainz b. Helen Hay Whitney Foundation c. NewYork–Presbyterian Hospital d. National Institutes of Health
Output:
a