In the following diagram, four different index fossils are labeled: Which of the labeled fossils comes from the youngest organism? A B C D

• WorldCitizen: If you look at the leftmost part of the graphic, it includes a time axis, where the top represents the most recent time and the bottom the earlier times, so just using this axis, we can see that the fossil A is the earliest, or the youngest, because it it the highest one. - This is the correct answer, fossil A. 
  
  Additionally, we could look at the periods - our fossil A is from the Jurassic period. we can compare it to the fossil B, which is from Permian period. Indeed, Jurassic is a younger age than Permian (or  Devonian and Cambrian, the ages of C and D) - so this confirms that A is the best answer. 
• kaibeth:

  Answer:

  A is from the youngest snail on the chart that snail is only a babay

  Explanation:

  Have a neato day! This question is important don't forget it....ever! *sigh ima of the tireds