Instructions are a set of commands or steps that tell a computer or a device what to do. They are essential for the proper functioning of software, hardware, and applications. The correct answer is option 'c' - program.

Explanation:
Instructions are necessary for the execution of any task, whether it is performed by a computer or a human. In the context of computers, instructions are written in a specific programming language and are known as programs. These programs are a set of instructions that are executed by the computer to perform a specific task.

Let's break down the answer into headings and bullet points for a better understanding:

1. Instructions and their importance:
- Instructions are a set of commands or steps that guide the computer or device on how to perform a specific task.
- They are like a recipe that provides clear directions to achieve a desired outcome.

2. Software, hardware, and applications:
- Software refers to a collection of programs, data, and instructions that tell a computer how to perform specific tasks. It includes operating systems, applications, and utility programs.
- Hardware refers to the physical components of a computer, such as the processor, memory, storage devices, input/output devices, etc.
- Applications, also known as software applications or simply apps, are specific programs designed for a particular purpose, such as word processing, gaming, or photo editing.

3. Programs as a set of instructions:
- Programs are sets of instructions written in a programming language.
- These instructions are processed by the computer's processor to perform a specific task or series of tasks.
- Programs can be written by software developers or users themselves, depending on the level of complexity required.

4. Examples of programs:
- A word processing program like Microsoft Word or Google Docs provides instructions for creating, editing, and formatting documents.
- A web browser like Google Chrome or Mozilla Firefox provides instructions for accessing and rendering web pages.
- An image editing program like Adobe Photoshop provides instructions for manipulating and enhancing images.

In conclusion, a set of instructions is called a program. Programs are written in a programming language and are executed by a computer or device to perform specific tasks. They are essential for the functioning of software, hardware, and applications.