Final answer:
The next component after ADD4 in the 802.11 MAC frame structure is the Frame Body, which varies in size and is followed by the Frame Check Sequence (FCS) for error detection.
Step-by-step explanation:
The student is asking about a component of the 802.11 MAC frame structure which is a standard for wireless networking. After the FC (Frame Control), DUR (Duration), three address fields (ADD1, ADD2, ADD3), SEQ (Sequence Control), and the optional ADD4 (fourth address field), the next component in the frame structure is the Frame Body followed by the Frame Check Sequence (FCS).
The Frame Body varies in size depending on the type (e.g., management, control, data) of the 802.11 MAC frame being used. The FCS is used to detect any errors that may have occurred during transmission.