A. The default value is the value of the environment variable$ORACLE_HOME;if$ORACLE_HOME isn't set,then the default is set to$ORACLE_BASE.
B. The default value is the value of the environment variable$ORACLE_BASE;if$ORACLE_BASE isn't set,then it is set to$ORACLE_HOME.
C. DIAGNOSTIC_DEST is always equal to$ORACLE_HOME.
D. DIAGNOSTIC_DEST is always equal to$ORACLE_BASE.
答案：（B）
解析：
《Concepts concepts》