Which of the following program infects the system boot sector and the executable files at the same time?

A stealth virus intercepts OS calls to hide its presence from antivirus tools but does not specifically target both the boot sector and executable files simultaneously.

A polymorphic virus mutates its own code with each replication to evade signature-based detection, which is a self-obfuscation technique unrelated to targeting multiple system components.

A macro virus embeds malicious macros inside document files such as Word or Excel and relies on the host application's macro engine to execute - it does not infect boot sectors.

A multipartite virus uses more than one infection mechanism - it infects the master boot record (MBR) or volume boot record to activate at system startup, and also appends to or overwrites executable files to spread via program execution. This dual-vector approach makes it harder to remove because cleaning only the boot sector or only the executables leaves the other infection path active and capable of re-infection.