According to the CHFI v11 Computer Forensics Fundamentals and File Analysis modules, identifying file types using file signatures (magic numbers) is a core forensic technique. File extensions can be easily manipulated by attackers as an anti-forensics tactic, so investigators rely on hexadecimal headers to determine the true file format.

The hexadecimal sequence 47 49 46 corresponds to the ASCII characters ''GIF''. This signature appears at the beginning of all Graphics Interchange Format (GIF) files and is typically followed by version identifiers such as GIF87a or GIF89a. CHFI v11 explicitly lists GIF file headers as a common example when teaching file signature verification using hex editors.

For comparison:

PNG files start with the signature 89 50 4E 47

BMP files start with 42 4D (ASCII ''BM'')

JPEG files typically start with FF D8 FF

Because the investigator observes 47 49 46 at the beginning of the file, this conclusively identifies the file as a GIF image, regardless of its filename or extension.

CHFI v11 emphasizes that hexadecimal signature analysis is essential when investigating disguised files, malware hidden as images, or data exfiltration attempts using file extension mismatch techniques.

Therefore, based on the file's hexadecimal signature, the image format is GIF, making Option C the correct answer.