World Wildlife Fund (WWF)and Greenpeace are two famous organizations in the world. They both aim at making our planet a better place to live.
    World Wildlife Fund works to protect wild animals and plants. It began in Switzerland on September 11,1961.Now,it has offices in 100 countries and nearly 5 millions members all over the world. The members are from different groups ,including governments, business, scientists and farmers. They have played an active role in saving animals and rainforests. One recent WWF project is protecting the Amazon rainforest. WWF has done plenty of research to find creative ways that meet the need of both people and nature.
    Greenpeace was set up in 1971,with an idea of working for world peace at the very beginning. Now it is active in protecting oceans, forests, and animals as well. It also calls for the use of clean energy, like wind power and solar power. Greenpeace has offices in 45 countries such as America and Canada. Its head office is in Netherlands. Greenpeace has about 3 million members at present. Small steps lead to big changes. It encourages more and more people to take action.

称取NaCl和BaCl₂的固体混合物32.5g，加入100g蒸馏水，完全溶解后向该混合溶液中逐滴加入质量分数为10%的Na₂SO₄溶液，反应生成BaSO₄沉淀的质量与所加入的Na₂SO₄溶液的质量关系如图所示．试回答下列问题：（提示：BaCl₂+Na₂SO₄═BaSO₄+↓+2NaCl）