Correct Option: D Explanation of Why Option D is Correct The main difference between a laptop and a desktop computer lies in their design and functionality, particularly regarding portability and power supply.

1. Portability: Laptops are designed to be portable, meaning they can be easily carried around. This portability is largely due to their built-in battery, which allows them to operate without being plugged into a power source. This is a significant advantage for users who need to work on the go, such as students, business professionals, or anyone who travels frequently.
2. Battery Capacity: Laptops contain high-capacity batteries that can power the device for several hours, depending on usage. This allows users to work, browse the internet, or watch videos without needing to be tethered to an electrical outlet. The battery life can vary based on the laptop's specifications, usage patterns, and power management settings, but it is a defining feature of laptops.
3. Desktop Limitations: In contrast, desktop computers are typically stationary and require a constant power supply from an electrical outlet. They do not have built-in batteries, which means they cannot operate without being plugged in. This makes them less convenient for mobile use but often allows for more powerful hardware configurations and better cooling systems.

Why the Other Options are Incorrect

• Option A: "does not have mouse while a desktop has"
• Explanation: This statement is misleading. Both laptops and desktops can use a mouse. Laptops often have a built-in touchpad that serves as a pointing device, but they can also connect to external mice via USB or Bluetooth. Desktops typically require an external mouse, but this does not define the fundamental difference between the two types of computers.
• Option B: "uses USB port while desktop uses parallel port"
• Explanation: This option is incorrect because both laptops and desktops commonly use USB ports. In fact, USB ports have largely replaced parallel ports in modern computing for both types of devices. Parallel ports are largely outdated and not a distinguishing feature of desktops compared to laptops.
• Option C: "can be connected to the internet while desktop cannot"
• Explanation: This statement is false. Both laptops and desktops can connect to the internet. Laptops often have built-in Wi-Fi capabilities, allowing for wireless internet access, while desktops can also connect to the internet via Ethernet or Wi-Fi if equipped with a wireless card. Therefore, this option does not accurately represent a key difference between the two.

Summary of Key Points

• Portability: Laptops are portable and can operate on battery power, while desktops are stationary and require a constant power supply.
• Battery: Laptops have high-capacity batteries that allow for extended use without being plugged in, a feature not present in desktops.
• Functionality: Both laptops and desktops can use mice and connect to the internet, making options A, B, and C incorrect.
• Design Purpose: Laptops are designed for mobility, while desktops are typically designed for performance and expandability.

This understanding of the differences between laptops and desktops is crucial for making informed decisions about which type of computer best suits your needs.