The time needed for a typical atom in an oceanic plate to complete a plate-tectonic cycle is ________ years.
A. about 10 million
B. about a million
C. about a hundred thousand
D. less than 500
E. in excess of 250 million
Answer: E
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The greatest surface warming is projected for which of the following regions during the next 100 years?
A. polar regions B. tropics C. middle latitudes D. equator
The cells that allow the immune system to respond more quickly to an antigen when it is encountered again later in life are called
A) innate immune cells. B) helper T cells. C) memory cells. D) killer T cells.
Groups living in close proximity to one another yet practicing uniquely different social customs suggests
A) refusal to teach other customs in schools. B) refusal to share other customs in religious ceremonies. C) inability to set up telephone service. D) limited connections due to topographic, linguistic or ethnic barriers. E) military confrontation.
The image below shows a beam of radiation passing between two electrically charged plates. 
Which of the beams is due to a high energy electron?
A. a B. b C. c D. all of the above E. none of the above