A、Absorb the waste gas. B、Adapt to the climate. C、Be a source of protein. D、Serve as a healing place. C短文中间部分指出，海洋为人类提供了氧气、调节气候，

A new system has been developed to measure the health of the world’s oceans. Scientists say the system will change the way we think about oceans and how they affect our lives. It is called the Ocean Health Index.(20)The index is designed to tell if anything is wrong with the oceans and, if so, what can be done about it. Greg Stone is chief ocean scientist for the environmental group Conservation International. He is also vice-Chairman of the Global Agenda Council on Oceans at the World Economic Forum.(21)According to Mr. Stone, the Ocean Health Index is the first global, totally scientific and transparent measure of ocean health that we’ve ever had. It will help end a lot of ignorance about the seas. No matter whether people live in the United States or in the middle of Africa, they should care about what happens to the oceans. Most of the oxygen that we breathe comes from the ocean. The oceans are the primary climate adaptation system. They absorb carbon.(22)Also, one out of four people on the planet get their daily source of protein from the ocean.
    The Ocean Health Index uses 200 separate measurements. Once a year, scientists will use it to announce whether the oceans successfully passed the test. People have looked to nature for medicines since ancient times. And modern scientists have searched the world’s rainforests for new medicines. But the ocean may be an even better source. At least 26 drugs that come from sea organisms are currently being used or developed. And a new generation of chemists hopes to increase that number.
20. What’s the Ocean Health Index designed for?
21. What is one of the distinguished features of the Ocean Health Index?
22. What can oceans do for people?