1aragraph 3: It is known that most sinkholes are caused by a build-up of water in the soil over a natural cavity in limestone rock. The saturated soil's weight causes the cavity's roof to collapse and all the earth above with it. But in this case, there's no limestone bedrock. In fact, there's no solid rock undemeath at all. The city is built on rather loose volcanic debris. What is believed to have happened here is that water leaked from the sewer system and caused the ground under the foundations of buildings to become hollowed out. Then at a certain point the ground just collapsed in this extraordinary pipe shape.
Paragraph 4: So strictly speaking, this isn't a real sinkhole. It's a different phenomenon that no one has a name for yet. Whatever you call it, the effect is both amazing and frightening. One local official said that it had happened after a freak tropical storm caused overload on the water system and that it is not expected to happen again. Local residents seemed less sure. One told me she wasn't waiting to find out. 'My family and I are getting out of here as soon as we can!'
Other sinkholes like this are known to exist and I'd be very interested to hear from any readers if you've seen anything similar.
QUESTIONS 1-5.
Write the best answer A, B, C or D in the box provided for each of the following questions:
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