Which three ESP fields can be encrypted during transmission? (Choose three.)

Which three ESP fields can be encrypted during transmission? (Choose three.)
A . Security Parameter Index
B . Sequence Number
C . MAC Address
D . Padding
E . Pad Length
F . Next Header

Answer: D,E,F

Explanation:

The packet begins with two 4-byte fields (Security Parameters Index (SPI) and Sequence Number). Following these fields is the Payload Data, which has substructure that depends on the choice of encryption algorithm and mode, and on the use of TFC padding, which is examined in more detail later. Following the Payload Data are Padding and Pad Length fields, and the Next Header field. The optional Integrity Check Value (ICV) field completes the packet.

Source: https://tools.ietf.org/html/rfc4303#page-14