Which of the Following Are True About OSI Model Data

Multiple Choice

Which of the following are true about OSI model data units? (Choose all that apply.)

A) an SDU has been passed down from a higher layer to a lower layer
B) encapsulation occurs when a higher layer adds headers to the PDU
C) an SDU at a given layer is the PDU of the layer below
D) a PDU will be sent to the peer layer at the receiving device