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What is the MAIN idea of the selection?
a) Michael Collins, Neil Armstrong and Buzz Aldrein flew on the largest rocket ever built.
b) In 1969, Michael Collins circled the moon, while Neil Armstrong and Buzz Aldrin walked on it.
c) Buzz Aldrin was supposed to be the first person to step onto the lunar surface on July 16, 1969.
d) Neil Armstrong and Buzz Aldrin measure the exact distance from the moon to Earth
B) In 1969, Michael Collins circled the moon, while Neil Armstrong and Buzz Aldrin walked on it.