题目内容：

    The ocean covers over 70 percent of the surface of Earth today, but over 3 billion years ago the entire planet may have been covered in water. To investigate what our planet was like billions of years ago, a team of researchers turned to indirect methods of analysis at a geological site in the Australian Outback known as Panorama(全景画) in the Pilbara Craton. Today, the region is 100 kilometers inland, but 3.2 billion years ago, it was deep underwater.

In fact, there were also once ancient hydrothermal vents (热水口) there where seawater bubbled up through the ocean floor. “There are no samples of really ancient ocean water lying around, but we do have rocks that interacted with that seawater and remembered that interaction,”  lead author Benjamin Johnson, an assistant professor at Iowa State University, said in a statement.

The researchers collected over 100 of these rock  samples and found something peculiar in them: a slightly higher amount of a particular isotope (同位素) of oxygen. The vast majority of oxygen on Earth is Oxygen-16 and contains eight protons (质子) and eight neutrons. However, about 0.20 percent is Oxygen-18.

Samples from Australia show the region’s ancient water contained more Oxygen-18 than present times. Since continents are covered in clay-rich soil that is efficient at trapping Oxygen-18, the team suggests that without continents covered in soil, more Oxygen-18 would have been present in the ocean. Their discovery indeed suggests there wasn’t much dry land available 3.24 billion years ago.

“There’s nothing in what we’ve done that says you can’t have tiny, micro -continents sticking out of the oceans,” added co-author Boswell Wing. “We just don’t think there were global-scale formations of continental soils like we have today.” The researchers don’t know when and how  continents began to emerge out of the ocean but they plan to investigate “younger” rock formations to piece together a more precise timeline.

1.Where is the research site?

A.In a region deep underwater.

B.In a region off Australia.

C.In a region inland Australia.

D.In a region outside the Pilbara Craton.

2.What do the underlined words “interact with” in Paragraph 2 mean?

A.Have an effect on each other. B.Have a one-way effect.

C.Have a mysterious effect. D.Have a negative effect.

3.What’s the researchers’ conclusion after analyzing samples from Australia?

A.Modern earth must have been a water world.

B.Modern earth must have been a continental world.

C.Ancient earth may have been a water world.

D.Ancient earth may have been a continental world.

4.What’s the researchers’ next focus of the study?

A.To research continental soils’ formations.

B.To research the ocean’s formations.

C.To research “older” rock formations.

D.To research “younger” rock formations.