正解:A
The file that is extractable via TCP stream within Wireshark is the one that has the Content-Type header set to application/octet-stream, which indicates binary data. This header is present in frames 7, 14, and 21, which are part of the same TCP stream. The other frames have different Content-Type headers, such as text/html or image/jpeg, which are not extractable as binary files. References := Understanding Cisco Cybersecurity Operations Fundamentals (CBROPS) v1.0, Module 3: Network Intrusion Analysis, Lesson 3.2: Analyze Data from Common TCP/IP Protocols, Topic 3.2.3: HTTP