Circumduction occurs when:

• A. a limb moves in a circular motion, combining flexion, extension, abduction, and adduction
• B. a joint moves only in one plane, such as flexion or extension
• C. the angle between two bones decreases
• D. a bone rotates around its own longitudinal axis

Answer: (A)

Verified step by step guidance

1. Step 1: Begin by understanding the term 'circumduction.' Circumduction is a movement pattern that involves a circular motion of a limb, combining multiple types of movements such as flexion, extension, abduction, and adduction.
2. Step 2: Analyze the options provided in the problem. Option 1 describes a limb moving in a circular motion and combining flexion, extension, abduction, and adduction, which matches the definition of circumduction.
3. Step 3: Evaluate the other options. Option 2 mentions movement in only one plane, such as flexion or extension, which does not align with circumduction as it involves multiple planes of motion. Option 3 describes a decrease in the angle between two bones, which is specific to flexion, not circumduction. Option 4 refers to rotation around a longitudinal axis, which is characteristic of rotational movement, not circumduction.
4. Step 4: Confirm that circumduction is a complex movement involving multiple planes and types of motion, distinguishing it from simpler movements like flexion, extension, or rotation.
5. Step 5: Conclude that the correct description of circumduction is the one that involves a limb moving in a circular motion, combining flexion, extension, abduction, and adduction.