Pei is an operating room nurse in charge of preparing the sterile field. Once she has prepared the sterile field, which of the following is acceptable for Pei
to do in order to protect it?

A. Pei bends down to pick up an instrument that fell on the floor,
removes the instrument from the operating room, and returns to
the sterile field.
B. Pei leans against the wall of the operating room in order to take a
break, and then she returns to the sterile field.
C. Pei leaves the operating room until the procedure begins to keep
any remaining pathogens on her from contaminating the sterile
field.
D. Pei stays in the operating room before the procedure begins to
ensure the sterile field is not left unattended.

explanation:

two years ago, when picking flowers in the mountains back of yosemite valley, i found a book. it was blotted and storm-beaten; all of its outer pages were mealy and crumbly. the paper seemed to dissolve like the snow beneath which it had been buried, however; many of the inner pages were well preserved. and although all were more or less stained and torn, whole chapters were easily readable. this is the condition of the great open book of yosemite glaciers today; its granite pages have been torn and blurred by the same storms that wasted the castaway book.two years ago, when picking flowers in the mountains back of yosemite valley; i found a book. it was blotted and storm-beaten, all of its outer pages were mealy and crumbly. the paper seemed to dissolve like the snow beneath which it had been buried, however, many of the inner pages were well preserved. and although all were more or less stained and torn; whole chapters were easily readable. this is the condition of the great open book of yosemite glaciers today, its granite pages have been torn and blurred by the same storms that wasted the castaway book.