The correct answer is B.
OBJ-2.7: The message contains a file attachment hoping that the user will execute or open it. The attachment’s nature might be disguised by formatting tricks such as using a double file extension, such as Invoice1043.pdf.exe, where the user only sees the first extension since .exe is a known file type in Windows. This would explain the black popup window that appears and then disappeared, especially if the exe file was running a command-line tool. This file is most likely not a PDF, so there is no need for a PDF reader. Additionally, most modern web browsers, such as Chrome and Edge, can open PDF files by default for the user. The file would not contain an embedded link since an embedded link is another popular attack vector that embeds a link to a malicious site within the email body, not within the file. This email is likely not spam and would be better categorized as a phishing attempt instead.