Final answer:
The riddle 'what asks no questions but must be answered' typically refers to a telephone or a doorbell, both of which signal when someone is attempting to communicate or get attention.
Step-by-step explanation:
The student's question, "what asks no questions but must be answered," is a type of riddle, which is a question or statement intentionally phrased to require ingenuity in ascertaining its answer. In this context, the answer to the riddle is typically the telephone or a doorbell, as both signal when someone is trying to get in contact or gain attention, and generally, one responds to them. Riddles can form part of the teaching in English, particularly when focusing on language play, word definitions, and understanding semantics. They can encourage students to pay attention to wording and to contemplate why certain expressions carry the meanings they do.