Answer A.
It can be inferred from the passage that if an object contains more carbon 14 than nitrogen 14, the object is …………
A. less than 5,570 years old
B. too old to be dated to carbon-14
C. contains too much radioactivity to be used by archaeologists.
D. over 5,570 years old.
Based on paragraph 2: “Carbon-14 has a half-life of 5.570 years, which means that after that number of years, half of the carbon-14 atoms have decayed into nitrogen-14. It is the ratio of carbon-14 in that substance that indicates the age of the substance. If, for example, in a particular sample the amount of carbon-14 is roughly equivalent to the amount of nitrogen-leaf, this indicates that around half of the carbon- 14 has decayed into nitrogen-14, and the sample is approximately 5,570 years old”: Carbon-14 has a half-life of 5,570 years, which means that after all these years, half of the carbon-14 atoms have decomposed to nitrogen-14. It is the ratio of carbon-14 present in the substance that indicates its age. For example, if in a particular specimen the amount of carbon-14 is equal to the amount of nitrogen-14, that indicates that about half of the carbon-14 has decomposed to nitrogen-14, and the specimen is dated. about 5,570 years old.
If an object contains more carbon 14 than nitrogen 14, then it has not completed its half-life of 5,570 years, so the object is less than 5,570 years old.