Which use of line is most suitable for showing a tall building as strong and stable?

Correct answer: Strong vertical lines

The correct answer is D: strong vertical lines. Vertical lines rise upward and are commonly associated with height, firmness and upright structure. In a drawing of a tall building, repeated strong verticals can reinforce the impression that the building stands straight and securely. They also echo the building’s actual architectural direction. A is not the best choice because wavy lines suggest softness, flexibility or movement rather than firm construction. B creates a broken, interrupted effect and is less suitable for communicating solid strength. C resembles drifting smoke, so it suggests irregular movement and uncertainty instead of stability. The answer does not mean that every building must be drawn only with vertical lines; it means that, among these choices, vertical lines best support the intended visual quality. Memory cue: vertical lines stand upright like pillars. Do not confuse height with speed: verticals suggest rising strength, while energetic diagonals more often suggest movement.