One of the most urgent environmental problems in the world today is the shortage of clean water. Having clean drinking water is a basic human right. However, acid rain, industrial pollution and garbage have made many sources of water undrinkable. Lakes, reservoirs and even entire seas have become vast pools of poison. Lake Baikal in Russia is one of the largest lakes in the world. It contains a rich variety of animals and plants, including 1,300 rare species that do not exist anywhere else in the world. Yet, they are being destroyed by the massive volumes of industrial effluent which pour into the lake every day. Even though laws have been made, the government does not have the power to enforce them. Most industries simply ignore the regulations. The Mediterranean Sea occupies 1% of the world’s water surface, but it is the dumping ground for 50% of all marine pollution. Almost 16 countries regularly throw industrial wastes a few miles off shore. Water is free to everyone. A few years ago, people thought that the supply of clean water in the world was limitless. Today, many water supplies have been ruined by pollution and sewage. Clean water is now scarce, and we are at last beginning to respect this precious source. We should do something now.

Câu 47: What’s the main idea of the reading text?

A. Laws have been made to prevent countries from polluting the environment.

B. Clean water is becoming scarce due to pollution and sewage.

C. Sea water is increasingly polluted by industrial wastes

D. People are throwing poisons into bodies of water.

Câu 48: What does foe word "It" in the passage refer to ______________.

A. sea                           B. pool                         C. Lake Baikal              D. plant

Câu 49: Which of the following is NOT a cause of undrinkable water.

A. acid rain                  B. deforestation         C. garbage                   D. industrial pollution

Câu 50: The word "marine" Is closest in meaning to ______________.

A. mountainous          B. underground           C. inland                      D.  aquatic