The dinosaurs in the late cretaceous period failed to survive on the planet because of factors such as inadequate food supplies, harsh weather, and an inability to adapt to the changing environment.

A. an inability
B. that they were unable
C. because they were unable
D. being unable
E. lacking an ability
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Official Solution:

The dinosaurs in the late cretaceous period failed to survive on the planet because of factors such as inadequate food supplies, harsh weather, and an inability to adapt to the changing environment.

A. an inability
B. that they were unable
C. because they were unable
D. being unable
E. lacking an ability

1. Correct. The sentence contains a list of factors that kept the dinosaurs from surviving on Earth: "inadequate food supplies, harsh weather, and an inability to adapt to the changing environment." In lists of examples, all the examples must be parallel (in the same form). The list has, as its elements, nouns, which are parallel. Thus, this choice contains no error. If you understand the list, this is a pretty straightforward parallelism question.
2. This choice a clause "that they were unable to communicate with Native Americans" is a part of the list instead of a noun, thus violating the parallelism.
3. As in (B) this choice is incorrect because "and because they were unable to adapt …." is a clause rather than a noun, thus violating the parallelism.
4. This choice is incorrect because "and being unable to ….." is a verb construction rather than a noun, thus violating the parallelism.
5. This choice is incorrect because "and lacking ability to …." is a verb construction rather than a noun, thus violating the parallelism.

Answer: A
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I agree with explanation. Just to remark that the explanation says
This choice a clause "that they were unable to communicate with Native Americans" is a part of the list instead of a noun, thus violating the parallelism.
Clearly from another question

I think this is a high-quality question and the explanation isn't clear enough, please elaborate. Why "an" inability and not "inabilities"?

I went for choice B
because there was a "coma"+"and" (..., and...) in choice A. The list format was: adj+noun ( inadequate food supplies, harsh weather) and underlined part seemed to distort the parallelism. Am I wrong

Hi, The sentence talks about factors because of which dinosaurs failed to survive.
Your observation is correct. All the list items are in structure as adj+Noun, but eventually it is a list of nouns. In choice B "that" modifies the entire clause "they were unable to..." and thus is not correct. In choice A it starts with noun "inability", even if it lacks adj, it still maintains list of nouns and it is correct.

The use of "and" here -
Whenever we have more than 2 elements in a list, We express them as x, y and z. "and" in this case is used in same sense and it is used to maintain the parallelism and not to distort.

Hope it helps..

I think this is a high-quality question and I agree with explanation.

AndrewN - could you please help me understand why in Option E "lacking" is not a "noun" that is acting as a gerund? The explanation says that "lacking an ability" is a verb, but I am not able to completely grasp why it is not a noun.
I often get confused in parallelism questions involving noun, gerund and '-ing' verbs.

Hello, Pankaj0901. If lacking an ability to adapt to the changing environment is an answer to the question, What is a factor that caused the demise of the dinosaurs? then the entire phrase is indeed a gerund and acts in the capacity of a noun. Note that if the same phrase were dropped into the sentence either in the beginning or after the dinosaurs, it would instead be acting as a modifier in the capacity of an adjective.

1) Lacking an ability to adapt to the changing environment, the dinosaurs in the late Cretaceous period failed to survive...
2) The dinosaurs in the late Cretaceous period, lacking an ability to adapt to the changing environment, failed to survive...

Finally, for the phrase to take on the role of a verb, we would expect to see a "helping" verb in the form of to be at the head:

3) The dinosaurs in the late Cretaceous period were lacking an ability to adapt to the changing environment and failed to survive...

I hope this information may prove useful to you down the road. Thank you for thinking to ask me.

- Andrew

Thank you AndrewN . Very nicely answered. I should not be confused with gerund or verb at least going forward.