In the question, one sentence is given and four words are given in bold denoted by (A), (B), (C) and (D). You have to decide which of the following is inappropriate in context. If all the words are appropriate in the context then mark ‘All correct’ as your answer.

Dinosaurs first appeared (A) during the Triassic period, although the exact origin (B) and timing of the evolution (C) of dinosaurs is the subject of active (D) research.