Explanation:

Let's analyze the definition of a computer virus and the given options: **Computer Virus Definition:** A computer virus is a type of malicious software program ('malware') that, when executed, replicates by inserting copies of itself into other computer programs, data files, or the boot sector of a hard drive. It typically requires a host program to spread. \nLet's evaluate the options:\nOption (A) **Software**: While a virus is indeed a type of software (it's a program), 'software' is a very broad term. It doesn't specifically capture the malicious and self-replicating nature of a virus. All applications and system files are also software.\nOption (B) **Malware**: This term is a portmanteau for 'malicious software'. It specifically refers to software designed to disrupt, damage, or gain unauthorized access to a computer system. A computer virus perfectly fits this definition, as its primary characteristic is malicious intent and self-replication. This is the most accurate classification.\nOption (C) **Application**: An application (or app) is a type of software designed to perform a specific function directly for the user or, in some cases, for another application. While a virus might be embedded within an application, the virus itself is not typically an application in the conventional sense; it's a malicious component. So, this is incorrect.\nOption (D) **System file**: A system file is a critical file that is part of an operating system or a core program. While a virus can infect or disguise itself as a system file to evade detection, a virus is not inherently a system file. Its definition is based on its behavior (replication, malicious intent), not its file type or location. So, this is incorrect. \nTherefore, the most precise and accurate term to describe a computer virus among the given options is 'Malware'. \nTherefore, the correct option is (B).