Hydrochlorofluorocarbons (HCFCs) are human-made chemicals that have been used as temporary replacements for chlorofluorocarbons (CFCs) in refrigerants because they decompose more readily in the atmosphere and thus pose less of a threat to Earth’s protective ozone layer. Levels of HCFCs have been measured in the stratosphere, and the concentrations of many different HCFCs have been steadily increasing since the mid- to late 1990s.
One important drawback of the use of HCFCs as a replacement for CFCs is that HCFCs:
a) biomagnify in food chains in the Arctic ecosystem
b) combine with water vapor to form acid precipitation
c) are greenhouse gases that contribute to climate change
d) react with carbon monoxide ( CO ) to form ozone in the troposphere

Choose the description that best matches each word. write the correct letter in the blank. 1. ostinato a. large, extended composition for chorus and orchestra 2. atonality b. full orchestra 3. musicology c. festive, march-like opening to a play or “semi-opera” 4. concerto d. small group of solo instruments 5. minimalism e. music contrasting a full orchestra and solo instruments 6. art song f. music played under the action to influence the mood 7. strophic form g. a vocal song focusing on artistic expression 8. incidental h. each stanza of a poem is set to the same music 9. oratorio i. repeated musical pattern that provides unity to a piece 10. dissonance j. steady beat; simple harmonies; short, repetitive melody 11. concertino k. harsh, unstable sounding of pitches; harmonic tension 12. tutti l. all 12 tones of chromatic scale, no tonal center 13. entrada m. the historical and scientific study of music