单项选择题
On Sunday, April 22, 1990, people all over the world celebrated the same holiday. It was the twentieth anniversary of Earth Day. The purpose of the holiday, which we celebrate every year on that date, is to help people learn how to protect the planet Earth. People around the world celebrate Earth Day because they worry about the planet. Many forms of animal life are disappearing from the earth. Carelessness and accidents in many countries have caused problems that are harmful to the environment. Air and water pollution, oil spills, and toxic waste are some of the serious problems.
In fact, protecting the earth is truly a worldwide issue. Pollution in one place often affects areas far away. For example, an accident in a nuclear power plant in one country can create a radioactive cloud that goes halfway around the world. Factory smoke in one country can cause acid rain in another. It is easy to see how our protecting the environment has become an international issue.
So, in order to begin the difficult job of saving the earth, people around the world did special things on Earth Day, 1990. In Japan, divers pulled garbage from the sea. In Nepal, hikers picked up trash on Mount Everest. Students marched in support of Earth Day in Hong Kong, and people planted medicinal herbs in the Philippines. In the United States, children planted trees. Native Americans told legends about the creation of the earth, artists drew pictures on walls next to highways, and musicians gave concerts to Support the work of environmental groups. Almost everyone everywhere stopped for a moment to think about how we can protect the earth.
A．Travelers cleared up rubbish on mountains.
B．Children planted trees.
C．Government officials made speeches in public to encourage people to do something for the earth.
D．Artists and musicians gave shows to support the environmental group's work.