Oracle9i extends the cursor sharing functionality with the new value of SIMILAR for the CURSOR_SHARING parameter. With CURSOR_SHARING = SIMILAR， cursors are shared for safe literals only. What is meant by ‘safe literals only’？（） 

• A、No literal value is substituted for a shared cursor. 
• B、Different execution plans are generated for substituted literal values. 
• C、The substitution of a literal value will produce different execution plans. 
• D、The substitution of any literal value will produce exactly the same execution plan.