The correct answer is (a). The eye is most sensitive to colors between red and green. This is because the human eye has three types of cone cells, which are responsible for color vision. These cone cells are most sensitive to red, green, and blue light. The cone cells that are most sensitive to red light are located in the center of the retina, while the cone cells that are most sensitive to green light are located in the periphery of the retina. This means that we are more sensitive to red and green colors when we look directly at them, and we are more sensitive to blue colors when we look at them out of the corner of our eye.
Option (b) is incorrect because orange is a mixture of red and yellow light. Option (c) is incorrect because green and blue are complementary colors. Complementary colors are colors that are opposite each other on the color wheel. When we look at complementary colors, our eyes are less sensitive to both colors. Option (d) is incorrect because yellow and green are both colors that are located in the middle of the color wheel. Our eyes are not more sensitive to colors that are located in the middle of the color wheel.