Most of the flowers in nature are red, orange and yellow. If we have seen a black flower, it's a chance in million. People have made a census (  ) to colors of more than four thousand kinds of flowers and discovered that only eight of them are black. As we know, sunlight is formed by seven different colored lights. The wave length of each light is different, so the quantity of heat in each light is also different. Flowers, especially their petals (  ) , are easy to be harmed by high temperature. Black flowers can take in all the light waves which cause the flowers to dry up in a high temperature. So black flowers can rarely survive sunlight. But red flowers, orange flowers and yellow flowers can protect themselves from sunlight by reflecting the red light, orange light and yellow light, each of which has a large quantity of heat. It is   _   to see a black flower.
impossible seldom common no chance