The correct answer is D. Glitch.
A glitch is a short-lived malfunction or disturbance in a system, especially in a computer or electronic device. It is a common term in the computer industry and is often used to describe a minor error or problem.
The other options are incorrect. A leech is a blood-sucking parasite that attaches itself to the skin of animals and sucks their blood. A squid is a cephalopod mollusk with a long, tapered body and ten arms. A slug is a slow-moving mollusk with a soft, slimy body.
Glitch is the most common and appropriate term to use to describe an error in software or hardware. It is a short, simple word that is easy to understand. It is also a neutral term that does not have any negative connotations.