What exactly is the question you are asking?
15. D is correct, exothermic reactions release heat
I am not sure about 16
B) O^2-
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Answer:carbon-14 levels in the atmosphere
Explanation:
When carrying out radiocarbon dating, the level of carbon-14 in a sample is compared with the level of carbon 14 in the atmosphere because, objects exchange carbon-14 with the atmosphere.
Comparison of the activities of carbon-14 in the atmosphere and in the sample gives the age of the sample since the half-life of carbon-14 is a constant.
Answer: gasoline, water, sea water, chloroform and mercury so B
Explanation: