Which brush movement is useful for showing a water surface with acrylic colour?

Correct answer: Light horizontal strokes

The governing concept is that the direction and character of marks can communicate form and movement. A calm water surface is generally read as broad and level, so light horizontal strokes suggest its surface plane, reflections, and gentle ripples. Therefore, option C is correct. Thick vertical lines suggest height, circular dots do not establish a level plane, and a black outline alone cannot show water’s reflective texture. Stroke direction should support the subject.