I have come across two GRE questions and the answer choices are in the form of a noun phrase. However, some carry an article while others do not. I do not understand the rules behind it. Here are the 2 questions.
1) According to the passage, improvement in brain function among early large mammals resulted from which of the following?
A. Interplay of predator and prey.
B. Persistence of free-floating awareness in animals of the grasslands.
C. Gradual dominance of warm-blooded mammals over cold-blooded reptiles.
As you can see, no choice above has an article. Is it right to say " the interplay of predator and prey" or "the gradual dominance of ...". These noun phrases seem pretty specific to me. So, why is there no article?
Now compared the above to this one:
2) According to the passage, as the process of arousal in an organism continues, all of the following may occur EXCEPT
A. the production of adrenaline
B. the production of norepinephrine
C. a heightening of sensitivity with respect to stimuli.
D. an increase in selectivity with respect to stimuli.
E. an expansion of the range of states mediated by the brain stem
As you can see, on the contrary, the choices in question B have an article. I just don't understand why there are articles in Question 2 choices and no articles in Question 1 choices.