___
A. It is the only accurate isotope for radiometric dating.
B. It represents most of the carbon in living things.
C. It has a half-life of almost 50 billion years.
D. It is used to estimate the age of carbon-based life forms.
___
A. He is preparing to suggest an answer to the question that he has just asked.
B. He is trying to encourage the students to answer a difficult question.
C. He is expressing doubt about the concept that he has been discussing.
D. He is probing to see whether the students have understood the lecture so far.
___
A. The lack of Vitamin D is the main cause of skin cancer.
B. Sunbathing for a long time causes no problems.
C. The danger of the sunshine has been ignored because of its benefits.
D. The advantages and disadvantages of the sun.
___
A. It changes ergo sterol to Vitamin
B. It suppresses serotonin.
C. It can cause Seasonal Affective Disorder.
D. It can cause skin and bladder cancer.
___
A. Some applicants were required to test an entrance examination to get admitted to the school.
B. Case studies became the main method of teaching.
C. Studying law became a 3 year endeavor.
D. Students should pass the comprehensive examination to graduate from the school.
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