Question

Both petroleum and coal are made up of complex carbon-based molecules, and both originated with living creatures of some kind. Both are vital sources of energy for the modern world and both were formed by geologic processes over millions of years. However, petroleum was mainly formed from the remains of ocean-dwelling microorganisms. Coal, on the other hand, originated from decayed vegetation in ancient swamps and bogs. In any case, it took millions of years for both coal and oil to be produced. This is the case because it took that much time for overlying sediments to produce the unimaginable heat and pressure that would one day allow us to harvest these energy resources. This passage uses a combination of comparison and contrast and     
  A. cause and effect.  
B. examples and explanations.
  C. supporting details.
  D. chronological order

Answer 1

I think the correct answer would be option A. This passage uses a combination of comparison and contrast and cause and effect.  The use of "both", "however" and "on the other hand" are indications that the passage is using compare and contrast principle. Also, it states several sentences that cause why these particular substance are formed for a longer time and what are  the processes involved like the phrase "because it took that much time for overlying sediments to produce the unimaginable heat and pressure". Along with this, the effect is stated. So, most likely, the passage above is also using the cause and effect organizing principle.