Odd-one-out – choose the word that does not belong with the others.

Introduction / Context:
Odd-one-out (classification) questions assess your ability to group items by shared properties and exclude the item that differs by type or function. Here, all four words relate to movement or control surfaces, but their categories differ.

Given Data / Assumptions:

• Options: wing, fin, beak, rudder
• Look for a common biological category versus a mechanical/artificial one.
• Consider the primary function of each item.

Concept / Approach:

Classify each word. Determine whether it is a natural anatomical part found on animals or a man-made device found on vehicles. Identify the one that does not fit the dominant category.

Step-by-Step Solution:

Verification / Alternative check:

Three options are anatomical parts of living organisms (wing, fin, beak). One option is a mechanical device (rudder). This makes “rudder” the unique outlier by origin and classification.

Why Other Options Are Wrong:

wing, fin, and beak all belong to the “biological anatomy” category and therefore share a common trait. None of these is man-made.

Common Pitfalls:

Grouping by function alone (e.g., steering) can mislead; both fins and rudders steer, but one is biological and the other is mechanical. Prioritize the broader categorical difference (natural vs. artificial).

Final Answer:

rudder