D. Korean Flag

It's design symbolizes the principles of yin and yang in Oriental philosophy. Note that the circle in the center of the flag is divided into two equal parts. The upper red section represents the positive cosmic forces of yang. Conversely, the lower blue section represents the negative cosmic forces of yin. The two forces together embody the concepts of continual movement and balance and harmony that characterize the sphere of infinity. The circle is surrounded by four trigrams in each corner. Each trigram symbolizes one of the four universal elements : heaven, earth, fire, and water.