Which statement is true regarding the creation of nested plans using Resource Manager？（）

• A、 Only one nested subplan is allowed.
• B、 The plans can be nested up to four levels.
• C、 Resource Manager does not support nested plans.
• D、 Nested plans control only the degree of parallelism but not the CPU.
• E、 Each nested plan gets a proportion of the CPU resources assigned to its parent group.