Direction: The following question, consists of an incomplete sentence or a sentence which is split into four parts. All four parts are jumbled up and are named as P, Q, R and S. These four parts are not given in their proper order. Arrange the jumbled parts of the sentence and find out which of the four combinations from the given options will correctly complete the sentence.

particularly in the last two decades or so the mouse (P) of choice for the entire spectrum of research (Q) has acquired the status of the experimental animal or the animal model system (R) in the post-genetic engineering era of modern biology (S)