A、They produce greenhouse gases by burning fuels. B、They pollute the environment by cutting plants. C、They add more and more was

TUVALU, a tiny country in the Pacific Ocean, has asked for help as it fears it will be swallowed up by the sea. Storms and huge waves are a constant threat and none of Tuvalu’s nine little islands is more than five meters above sea level. Salt water is already entering the country’s drinking water supply, as well as damaging plants that produce fruit and vegetables. Without urgent help, the country’s days are numbered. But Tuvalu is not the first place to face sinking into the sea. Venice, a historic city in Italy best known for its canals, has sunk about 24cm over the past 100 years. Experts say that it will have sunk another 20-50cm by 2050. A century ago, St. Mark’s Square, the lowest point in the city, flooded about nine times a year. Nowadays, it happens more than 100 times. While Venice is slowly sinking into the mud on which it stands, Tuvalu’s rising sea level is caused by global warming. The average global temperature has increased by almost 0.5 degree centigrade over the past century. Scientists expect it to rise by an extra 1-3 degrees over the next 100 years. Warmer weather makes glaciers melt, adding more water to the ocean. The warmer temperatures also make water expand, so it takes up more space, causing the sea level to rise. The sea level has risen about 10-25cm in the last 100 years. The main cause of global warming is human pollution. Through burning coal, oil and gas, people have been increasing the greenhouse gases in the atmosphere, such as CO₂. This adds to the power of the greenhouse effect, making the planet even warmer.
23. How is Tuvalu endangered?
24. What is the problem with St. Mark’s Square?
25. Why are human beings responsible for the mentioned disaster?