The correct answer is 'strings -a suspiciousfile.exe' because it leverages the 'strings' utility to search through all sections of the binary file ('suspiciousfile.exe') and extract ASCII strings. The '-a' option tells strings to output all strings, which includes those from all sections of the file. This output can reveal code snippets, error messages, or other indicators of the file's purpose or origin. 'strings -u suspiciousfile.exe' is incorrect because it only extracts Unicode strings, which might miss important ASCII strings. 'grep 'http' suspiciousfile.exe' is incorrect because it simply searches for the occurrence of 'http' within the binary without proper string extraction. 'file suspiciousfile.exe' is incorrect because it identifies the file type rather than extracting strings.