Which of the following statements is true? a. all natural radiation is at a level low enough to be safe. b. most of the nuclear radiation you are exposed to in the environment is man-made. c. you are exposed to nuclear radiation every day. d. naturally occurring nuclear radiation is called background decay.

A. All natural radiation is at a level low enough to be safe

the first american roller coaster was the mauch chunk switchback railway, built in the mountains of pennsylvania in the mid-1800s. the track, originally built to send coal to a railway, was reconfigured as a "scenic tour."

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