阅读下列短文，从每题所给的四个选项 （A 、B 、C  和 D ）中，选出最佳选项。

    My friend Jennie Crossen gave her bone marrow (骨髓) to a 51-year-old woman with leukemia, a woman she has never met.

    At the end of March, the Red Cross called back. Six different blood elements were tested; Jennie matched five completely and was about a 3/4 match of the sixth. So she was the best match.

    In April, Jennie went for a complete physical exam by one of the doctors who would perform the surgery. The doctor had to make sure that it would be no threat to her. The doctor told her that the surgery would entail having two quarts of bone marrow extracted from her hip bones. Jennie would probably be released the same day the surgery took place and should expect to be sore for a couple of months.

    "I didn't think it was that big a deal until I realized I was a match," Jennie said, "There wasn't a question in my head. It didn't seem like something that was going above and beyond."

    Jennie was left with two very small scars on her lower back from the surgery and was given medication to help dull the pain. She still felt a great deal of pressure on her lower back. "Being only 21, I feel like I am not old enough to significantly impact someone's life," Jennie said, "It seems strange to me that I could possibly save this woman's life which was being cut short by cancer."

    Three weeks after the surgery, Jennie received a call from the Red Cross representative who told her the transplant was successful. "I feel good, and I think it will actually work for her," she said, "So many people say they'd only donate if it was for a family member or close friend. This woman is someone's family and someone's friend. Obviously, no one she knows is a match, and the fact that you'd be able to help a perfect stranger is great."

阅读理解

        Washington: NASA has announced evidence that Jupiter's largest moon, Ganymede, has a saltwater ocean under its icy surface. The ocean seems to have more water than all the water on Earth's surface, according to new Hubble observation.

         New Hubble observations of Ganymede's magnetic field strongly suggest that the moon, which is the largest in our whole solar system, is home to a subsurface ocean.

        Scientists estimate the ocean is 95 kilometers thick, which is about 10 times deeper than Earth's oceans. But unlike our salty waters, Ganymede's ocean is buried under 150 kilometers of ice.

         While scientists have speculated(推测) since 1970s about the presence of an ocean on Ganymede—the largest moon in our solar system—until now the only observational evidence came from a brief flyby by the Galileo spacecraft, which didn't observe the moon long enough to confirm a liquid ocean.

         This discovery marks an important milestone, highlighting what only Hubble can accomplish. In its 25 years in orbit, Hubble has made many scientific discoveries in our own solar system. A deep ocean under the icy surface of Ganymede opens up further exciting possibilities for life beyond Earth.

        Scientists have already confirmed the existence of an ocean on Europe, another moon orbiting Jupiter, and NASA has announced plans to send an unmanned mission there searching for the life that might come with liquid water.

       Hubble is a telescope that orbits Earth, but because of its impressive gravitational analyses it can be used to study the inside of far distant planets. Using these same principles, scientists could theoretically detect oceans on distant planets as well.

体循环和肺循环之间的关系是（   ）