By analyzing the level of radioactive decay within a fossil specimen, scientists can establish the age of that fossil with a high degree of precision.When radioactive elements aren't present, scientists turn to __ analysis of Earth's sediment layers (strata)-to estimate how old a fossil is based on the age of the strata in which the fossil is found. Which choice completes the text so that it conforms to the conventions of Standard English? A. stratigraphy-the B. stratigraphy (the C. stratigraphy: the D. stratigraphy, the

## Step 1<br />The problem is a test of punctuation and grammar in English. The sentence is discussing two different methods used by scientists to estimate the age of fossils: one method involves analyzing the level of radioactive decay within a fossil specimen, and the other method involves analyzing the Earth's sediment layers (strata).<br /><br />## Step 2<br />The sentence is structured in a way that it is discussing two different methods, and the second method is introduced with a dash. The dash is used to separate the two methods and to indicate that the second method is a continuation of the first.<br /><br />## Step 3<br />The sentence is also structured in a way that it is discussing the age of the strata in which the fossil is found. The word 'the' is used to refer to the strata that have already been mentioned in the sentence.<br /><br />## Step 4<br />Given the above analysis, the correct choice is 'C. stratigraphy: the'. The colon is used to introduce the second method, and the word 'the' is used to refer to the strata that have already been mentioned in the sentence.