Which statement about Automatic Memory Management with Oracle 11g is true？（）  

A、 You cannot specify MEMORY_TARGET if you explicitly specify SGA_TARGET or  PGA_AGGREGATE_ TARGET values that are greater than zero in your parameter file.

B、 Oracle can reallocate memory between the SGA and PGA automatically as needed.

C、 To use Automatic Memory Management， you must explicitly set both the MEMORY_TARGET and MEMORY_MAX_TARGET parameters in your parameter file.

D、 You can set the MEMORY_TARGET parameter to a maximum value of the current SGA size plus the current PGA size.