Answer: Headers
Step-by-step explanation:
SYN segment is known as synchronization and the SYN sends the signal and then sending the a request to the server. The synchronization segment only include header and it does not carry any type of the data field as, the information are basically convey in the form of opening connection.
The SYN message only include the ISN number of the client as ISN is the initial sequence data number. And it also does not include any trailers.