Application of Skills Directions: Apply the Knowledge You Have Gained from Chapter 10

question 13

Multiple Choice

Application of Skills
Directions: Apply the knowledge you have gained from Chapter 10 to select the best answer to the questions about the following reading passage.
Invisible Threat
¹Any electrically charged conductor generates two kinds of invisible fields: electric and magnetic. Together they're called electromagnetic fields (EMFs) . For years, these fields, produced by household appliances, home wiring, lighting fixtures, electric blankets, and overhead power lines, were considered harmless. However, epidemiological studies have revealed a link between exposure to high-voltage lines and cancer (especially leukemia, a blood cancer) in electrical workers and children.
²Laboratory studies on animals have shown that alternating current, which changes strength and direction 60 times a second (and electrifies most of North America) , emits EMFs that may interfere with the normal functioning of human cell membranes, which have their own electromagnetic fields. The result may be mood disorders, changes in circadian rhythms (our inner sense of time) , miscarriage, developmental problems, or cancer. Researchers have documented increases in breast cancer deaths in women who worked as electrical engineers, electricians, or in other high-exposure jobs, and a link between EMF exposure and increased risk of leukemia and possibly brain cancer.
³The National Institute of Environmental Health Sciences concluded that the evidence of a risk of cancer and other human disease from the electric and magnetic fields around power lines is "weak." This finding applies to the extremely low frequency electric and magnetic fields surrounding both the big power lines that distribute power and the smaller but closer electric lines in homes and appliances. However, the researchers also noted that EMF exposure "cannot be recognized as entirely safe." Clearly, these invisible magnetic fields are more dangerous than we know, and we must stop being so complacent. We need to urge our congressmen to support research into the effects of electromagnetic fields and to propose stringent measures to keep us safe from this type of exposure.
-adapted from Hales, An Invitation to Health , p. 458
According to other clues in the sentence, the phrase circadian rhythms means

• A) electrical currents
• B) internal sense of time
• C) EMFs
• D) all of the above