Problem: Brad and Joe studied atmospheric conditions on different planets of our solar system. Joe studied about Earth, while Brad studied more about Venus. Which person learned about the planet with a thinner atmosphere?

A: Joe

Problem: Two neighboring lands experienced different climates. In Iceland, the actions of its people lead to a loss of animal and plant species. Denmark tried to keep the environment untouched as they understood its importance and the climate was unaffected. Which country has to do less ecological restoration?

A: Denmark

Problem: The Danube and Volga rivers both form large deltas, but the Danube river delta is larger and grows faster every year. Which river experiences a less significant decrease in flow velocity when it reaches the sea?

A: Volga

Problem: John liked studying about the planets in our solar system. He recently studied and made comparisons between Earth's and Venus's atmosphere. He was amazed with what he found out. Which planet has fewer clouds made of sulfuric acid?

A:
Earth