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

A stealth virus uses rootkit-like techniques to intercept OS calls and hide its presence from antivirus scanners, but does not specifically define a dual boot sector and file infection strategy.

A polymorphic virus mutates its own code or encryption routine with each replication to evade signature-based detection, which is an evasion technique independent of what it infects.

A macro virus embeds itself in document macros (e.g., Microsoft Office files) and executes when the document is opened - it does not infect boot sectors.

Multipartite viruses use a hybrid infection strategy - they infect the master boot record or volume boot record (activating at system startup before the OS loads) and also attach themselves to executable files (activating when infected programs are run). This dual-infection mechanism makes them more persistent and harder to remove because cleaning only one infection vector leaves the system reinfected from the other.