Answer the following question given this paragraph: 

rem = rad × factor where factor is a number greater than or equal to 1 that takes into account the type of radioactive emission and sometimes the type of tissue being exposed. For beta particles, the factor equals 1. For alpha particles striking most tissues, the factor is 10, but for eye tissue the factor is 30. Most radioactive emissions that people are exposed to are on the order of a few dozen millirems (mrem) or less; a medical X-ray is about 20 mrem. A sievert (Sv) is a related unit and is defined as 100 rem. What is a person’s annual exposure to radioactivity and radiation? Table 15.3 "Average Annual Radiation Exposure (Approximate)" lists the sources and annual amounts of radiation exposure. It may surprise you to learn that fully 82% of the radioactivity and radiation exposure we receive is from natural sources— sources we cannot avoid. Fully 10% of the exposure comes from our own bodies—largely from carbon-14 and potassium-40. Table 15.3 Average Annual Radiation Exposure (Approximate).


Q: Most radioactive emissions that people are exposed to are on the order of a few dozen what?

 Choices:

- ticks

- micrograms

- millivolts

- millirems

A:
millirems
