What is the sky filled in the blanks?

High blue sky, soft white sky, white and soft sky, high and transparent sky, high and big sky, thunder and lightning sky, deep blue sky, quiet and sunny sky

High blue sky, soft white sky, white and soft sky, high and transparent sky, high and big sky, thunder and lightning sky, deep blue sky, quiet and sunny sky, blue and vast sky.

The sky is empty; The vast space where the sun, moon and stars are listed. It is an important part of the earth. There is an ancient saying in China that the sky is round and the earth is round. People can observe meteorological or astronomical phenomena in the sky, so as to know the change of weather, the passage of time or their position. You can know the time of day at sunrise and sunset, and the moon's profit and loss for a month at night. The big dipper can indicate the north. The thickness and shape of clouds can judge whether it will rain or not. You can enjoy many beautiful phenomena in the sky, such as rainbow, aurora and meteor shower. Birds can fly in the sky. Due to the increasing use of fossil fuels such as oil, especially fuels such as coal that will release sulfur dioxide after burning, the visibility of the sky is gradually decreasing from 1973, except in Europe.