Multiple choice

Dinosaur fossils have been discovered in locations all over the earth, but the highest density of fossils has been found in areas, which have experienced few volcanic eruptions. The higher number of fossils discovered in stable regions can only be accounted for by the lack of destructive volcanic eruptions in those areas.

Which one of the following is a necessary presupposition of the argument above?

  1. A fossil that forms in the exact location of a previously formed fossil will eliminate the structure of the earlier fossil.

  2. The rate of volcanic eruptions within a given area varies greatly over time.

  3. The rate of fossil formation has dramatically increased recently.

  4. Fossil formations have been distributed fairly evenly over Earth during course of its history.

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The argument concludes that the reason for higher density of fossils in certain areas is that there has been less volcanic activity in those areas. This assumes that there is no alternate cause for the highest density of fossils being found in stable areas. Answer choice (D) confirms this assumption: fossil formations have been distributed evenly, so the difference in the number of fossils found is not due to an initial uneven distribution.

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