Configuration management is the process of managing change in hardware, software, firmware, documentation, measurements, etc. As change requires an initial state and next state, the marking of significant states within a series of several changes becomes important.The identification of significant states within the revision history of a configuration item is the central purpose of （） identification.

A．baseline

B．value

C．cost

D．control

* * 脓肿切开引流，为避免损伤乳管而形成乳瘘，应作____切开，乳晕下脓肿应沿乳晕边缘作____切口。急性乳腺炎的预防，关键在于____、____、____、____、____。