According to the passage, which of the following is TRUE？
A. Freedman and his colleagues hired 400,000 Americans to collect data.
B. About four hundred thousand Americans worked for Freedman"s team full time for 13 years.
C. People who took part in Freedman"s research are about 50 to 70 years old.
D. People who are 50 to 70 years old seldom drink coffee.
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