Answer:
Option D
Explanation:
(D) The use of the conjunction although implies that there is contradiction in sense within the sentence. The second part says that fear and aggression are distinct (meaning different) both physiologically and psychologically. In order to bring out the implied contrast the missing word must describe a state in which these two are quite similar or lack distinctiveness. The only possible words among the choices are simultaneous and transitional. Between the two, the word simultaneous must be ruled out because, in that case, the phrase must read 'simultaneous states of fear and aggression, and 'not simultaneous states between fear and aggression'. The word transitional refers to a stage of movement from one state to another when the qualities of both states are present together and the difference between them is blurred. It is this word which fits in logically in the given sentence, and is the answer.
