(5) When did the Earth form? (a) 10 billion years ago (b) 4.6 billion years ago (c) 446 million years ago (d) 6,000 years ago (6) On average, how do high clouds affect the surface temperature (compared to a clear sky)? (a) High clouds warm the surface by increasing the greenhouse effect (b) High clouds cool the surface by increasing the energy emitted to space (c) High clouds cool the surface by increasing the albedo (d) It depends on whether they are comprised of ice or liquid water

(5) The correct answer is (b) 4.6 billion years ago. The Earth formed approximately 4.6 billion years ago, based on radiometric age dating of rocks and minerals, as well as the ages of the oldest known terrestrial rocks.<br /><br />(6) The correct answer is (b) High clouds cool the surface by increasing the energy emitted to space. High clouds, such as cirrus clouds, have a cooling effect on the Earth's surface because they reflect incoming solar radiation back into space, reducing the amount of heat that reaches the surface. Additionally, high clouds can increase the amount of energy emitted from the Earth's surface to space, further contributing to the cooling effect.