What is the purpose of using a null timing (dejitter buffer)?

What is the purpose of using a null timing (dejitter buffer)?

A.
To hold the data temporarily so a CRC can be performed

B.
To queue incoming traffic from the CPE so that the SAR function can be performed

C.
To accommodate statistic collection on the interface card

D.
To smooth out any artificial gaps in the traffic before delivering the bits to the CPE device