Depicting items in contrasting colors, shapes, or sizes a. emphasizes differences b. confuses audiences c. highlights similarities d. imposes visual parallelism e. achieves balance

a. emphasizes differences.  
the basic concept of contrast making different from others. It can be done by changing any of the attributes of the objects like color, shape or size etc. In color it can be done by giving contrast colors like red, blue, black etc. In shapes it can be done by giving different shapes like cube ,cylinder,square etc. If you give colors with less difference it will be difficult to differentiate and confusion will occur.