单选题

　　 【填句补文】 Although the researchers have only just made the technical details of the microscope public, it is already on sale. It is currently the size of a refrigerator and takes several minutes to scan a circuit, but Xiao and Schrag are working ________.

　　 A、to take tiny chips we require

　　 B、to making chips any smaller

　　 C、to shrink it to the size of a desktop computer and cut the scanning time to 30 seconds

　　 D、of conducting electricity