Explanation:

The question asks for a term that describes a device connected to the motherboard. This implies components that are physically housed within the computer case and interface directly with the motherboard. Option A, 'External device', refers to components that are connected to the computer from the outside, such as a keyboard, mouse, monitor, or external hard drive. These are not typically described as being 'connected to the motherboard' in the sense of being *part of* the internal system directly plugged in. Option B, 'Adjunct device', is not a standard technical term in computer hardware for components connected to the motherboard. Option C, 'Peripheral device', is a broader term that refers to any auxiliary device that connects to and works with the computer, but is not part of the core computer architecture (CPU, main memory). This category can include both internal (e.g., internal hard drive, graphics card) and external devices. However, the Hindi translation "परिधीय (बाह्य) यंत्र" explicitly suggests an "external peripheral device", which would make it incorrect for devices *inside* the case. Option D, 'Internal device', specifically refers to components that are located inside the computer case and are connected to the motherboard. This includes a wide range of components such as RAM modules, the CPU, expansion cards (like graphics or sound cards), internal hard drives, and SSDs. This term accurately encompasses devices that are physically inside and directly connected to the motherboard. Therefore, 'internal device' is the most fitting description for a device connected to the motherboard and residing within the computer's casing.