题目内容：

    The COVID-19 pandemic has spread far and wide. Because of this, countries around the world have carried out containment measures to help stop the virus in its tracks. As more and more people stay inside to stay safe, the outside world seems to have become much quieter. In fact, scientists have seen this change in their research, too.

Seismologists—scientists who study earthquakes—have heard a lot less seismic (地震的) noise recently. Seismic noise is made from vibrations (震动) in the ground that are caused by things like ocean waves and human activity, such as construction work and traffic.

Thomas Lecocq, a scientist at the Royal Observatory of Belgium, located in Brussels, was the first to notice this phenomenon. According to Lecocq, the amount of seismic noise in Brussels has been reduced by about 30 to 50 percent since mid-March. Interestingly enough, this is around the same time Belgium started its containment measures.

Because of this reduction in background noise, scientists like Lecocq have been able to pick up on smaller earthquakes that some seismic stations—like the one in Brussels—wouldn’t have been able to before.

This phenomenon isn’t unique to Brussels, though. Once Lecocq shared his findings online, seismologists from all over the world echoed similar findings. Celeste Labedz, a graduate student at the California Institute of Technology, mentioned in a tweet that Los Angeles also experienced less background noise. “The drop is seriously wild,” she wrote. Researchers from the UK, France and New Zealand also noted a decrease in background noise since containment measures were put in place.

These global efforts to contain the COVID-19 virus have helped to shed light on seismic activity that may have gone unnoticed. It also shows that people are listening to health officials and following lockdown guidelines.

1.What did seismologists find out recently?

A.More smaller earthquakes are likely to happen.

B.Less seismic activity has been detected recently.

C.Reduced seismic vibration makes Earth quieter.

D.Seismic noise is caused by vibrations underground.

2.What can we learn from the text?

A.More seismic noise is being picked up.

B.More data on smaller earthquakes is being collected.

C.Scientists will shift their focus to smaller earthquakes.

D.Future big earthquakes can be more accurately predicted.

3.What does the underlined word “echoed” in paragraph 5 mean?

A.Questioned. B.Demanded.

C.Explored. D.Repeated.

4.What can we conclude from the last two paragraphs?

A.The drop in seismic noise is unique to Europe.

B.Seismic noise is mainly caused by human activity.

C.Many seismologists wanted tighter restrictions for their research.

D.The phenomenon proved that people are practicing social distancing.