4 Fortunately, the radiocarbon dating technique, developed in 1949 by Willard F.Libby, helped to resolve these problems. When 14C, which is naturally present in very small quantities in the air, is absorbed by living organisms, some of it remains in their tissues. 14C is created in the upper atmosphere where it unites with oxygen and transforms into carbon dioxide (CO2). In this form, it is integrated into the Earth's ecology, as plants absorb carbon dioxide from the air and pass along the 14C to organisms higher up in the food chain; animals devour plants, taking in 14C, and humans in turn consume both. Throughout an organism's life cycle, it constantly takes in 14C. A When living things die, however, 14C stops being absorbed, and the amount inside the dead organism begins to decay. B [8] Libby found that by measuring the amount of 14C that was left in organic material, the age of the subject could be estimated, as the rate of decay, or half-life of 14C, is gradual yet steady. Various radioactive substances have different rates of decay, ranging from seconds to thousands of years. D In the case of 14C it takes 5,730 years for half of the initial quantity of the 14C that was absorbed by an organism to disappear after it has died. It takes another 5,730 years for half of the remaining half to decay, and so on. This means if Libby discovered that 14C from an organic sample gave off half as much radiation as modern 14C, he could estimate the sample to be approximately 5,730 years old.
What can be inferred from paragraph 4about the rates of decay of
some radioactive substances?
A) They are too fast to be useful for dating purposes.
B) They do not have half-lives.
C) They are more consistent than 14C.
D) They are too difficult to calculate.
A가 답이고 밑줄친부분이 근건데요
ranging from seconds 해석도안되고 ㅠㅠㅠㅠㅠ
a가왜답인지도모르겠어요.....
저는 c를골랐는데 c는왜안되나요? 고수님들 부탁드려요!!!