Which of the following statements are true regarding N-tier architecture?

Which of the following statements are true regarding N-tier architecture? (Choose two.)

A.
Each layer must be able to exist on a physically independent system.

B.
The N-tier architecture must have at least one logical layer.

C.
Each layer should exchange information only with the layers above and below it.

D.
When a layer is changed or updated,the other layers must also be recompiled or modified.