Scientists use proxies to study climate in order to measure
A) current levels of carbon dioxide.
B) changes in temperature over the past 100 years.
C) changes in the ozone layer over the past 30 years.
D) climates hundreds and thousands of years ago.
D
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Why do you think that most cetaceans use sound for communication and echo-location?
a) Sound travels farther through water than light b) The ancestors of these organisms had vocal chords, so they adapted to project sound in water c) Cetaceans have ears so they can hear sounds that fish cannot d) Cetaceans have developed a simple language for communication e) Cetacean skulls are specially adapted for sound transmission
An electrical device that is "grounded" has
A. no potential difference between it and the ground. B. an infinite potential difference between it and the ground. C. low voltage. D. a firm connection to the ground.
A warm northward flowing ocean current is found along the east coast of the United States and a cold southward moving current is found along the west coast
Indicate whether the statement is true or false
After aerobic waste decomposition in a landfill has stopped,
A. anaerobic decomposition produces different gases, including methane. B. methane production also ceases in the absence of oxygen. C. no further breakdown of wastes occurs. D. further leachate is harmless.