The correct answer is A. 127.
USB (Universal Serial Bus) is an industry standard that defines the physical connection and protocol used for connecting peripheral devices to computers. USB was designed to replace the serial and parallel ports that were commonly used in computers at the time.
USB supports up to 127 devices on a single bus. This means that you can connect up to 127 devices to your computer using USB cables.
The 127 device limit is due to the way that USB addresses devices. Each device on a USB bus is assigned a unique address. The first 127 addresses are reserved for devices that are connected directly to the computer. The remaining addresses can be used for devices that are connected to hubs.
A hub is a device that allows you to connect multiple USB devices to a single USB port on your computer. Hubs can be either self-powered or bus-powered. Self-powered hubs have their own power supply, while bus-powered hubs draw power from the computer.
If you need to connect more than 127 devices to your computer, you can use a USB hub. However, you should keep in mind that the performance of your computer may be affected if you have too many devices connected.
The options B, C, and D are incorrect because they do not represent the maximum number of devices that can be connected to a USB bus. Option E is incorrect because it is not a valid option.