Where to dimension cylindrical features: For an external cylinder (such as a shaft), the diameter should be dimensioned in the view where the shape appears as a true circle rather than as a rectangle. Confirm this rule.

Introduction / Context:
Cylindrical parts appear as circles in one principal view and as rectangles in another. Drafting standards encourage placing diameter dimensions in the view where the feature is seen as a true circle for maximum clarity and to avoid ambiguity in interpreting size vs. length.

Given Data / Assumptions:

• An external cylinder (e.g., shaft) is present.
• One principal view shows a circular end; an adjacent view shows a rectangular side.
• Standard dimensioning practices apply.

Concept / Approach:
Dimension the diameter in the view where the circle is visible (true shape). Length or other axial dimensions may be shown in the side view. This separation aligns with best practices: use the most descriptive view for each dimension and minimize confusion between diameter and linear length features.

Step-by-Step Solution:

Verification / Alternative check:
Examine standard examples in drafting texts: holes and external diameters are dimensioned in the circular view to show true diameter. The side view supports lengths and locations of shoulders or steps.

Why Other Options Are Wrong:

• Using the rectangular view for diameter sacrifices clarity and invites mistakes.
• Splitting a single diameter across two views is unnecessary and cluttered.
• General notes are not a substitute for clear view-specific dimensions.
• Discouraging the circular view contradicts standard conventions.

Common Pitfalls:
Putting a diameter in the side view as a width dimension; omitting the diameter symbol; mixing length and diameter callouts in one cluttered view.

Final Answer:
Correct: dimension in the circular view where the diameter is seen true