Software quality assurance is now an (50) sub-discipline of software engineering. As Bucldy and Oston point out, (51) software quality assurance is likely to lead to an ultimate (52) of software costs. However, the major hurdle in the path of software management in this area is the lack of (53) software standards. The development of accepted and generally applicable standards should be one of the principal goals of (54) in software engineering.
53（）
A．usable
B．usage
C．useless
D．useness