Find out the odd word from the following four options:

Concept: In a classification (odd-one-out) question, three of the four items share a common category, and the correct answer is the one item that does not belong to that category, even if all four look alike on the surface (for example, sharing the same prefix).

Application: All four words here begin with the prefix "micro-", so the prefix itself cannot be the basis for grouping. Look instead at what each word actually denotes:

• Microfilm — a photographic reproduction of documents or printed pages recorded at a greatly reduced size on a roll or sheet of film, used for long-term archival storage.

• Microphone — an electro-acoustic device that converts sound waves into an electrical signal, used for amplification, recording, or transmission of audio.

• Microscope — an optical or electronic instrument that magnifies very small objects, used to examine specimens in a laboratory.

• Microbe — a microscopic living organism, such as a bacterium, virus, or fungus, studied in biology and medicine.

Cross-check: Grouping the words by what they actually are (not by spelling) shows that Microfilm, Microphone, and Microscope are all man-made technological objects or media used for recording, transmitting, or observing information, while Microbe is a living organism. Since three words share the "man-made technological object" category and one does not, Microbe is the odd word out.