What field in a TCP segment is used to determine if an arriving data unit exactly matches the data unit sent by the source?

In a TCP segment, the field used to determine if an arriving data unit exactly matches the data unit sent by the source is the Sequence Number field. This field indicates the position of the first byte of data in the segment, allowing the receiver to check if it received the correct data in the expected order. Additionally, the Acknowledgment Number field can confirm receipt of segments by indicating the next expected byte.