Could it be time to say goodbye to Earth? According to NASA, a giant asteroid is heading for Earth n

阅读理解C
Could it be time to say goodbye to Earth? According to NASA, a giant asteroid is heading for Earth next month. Well, when we say heading for Earth, we actually mean its heading for Earth’s vicinity（周边）, passing within 3,908,791 miles of our planet.
Officially classified as 52768 (1998 OR2), the near-miss has been predicted to occur on April 29. According to NASA, the asteroid is traveling toward us at 19,461 miles per hour and is about half the size of Mount Qomolangma.
The space agency first discovered the object in 1998 and said it would be “large enough to cause global effects” if it were to hit Earth. But despite being classed as “potentially hazardous （有危险的）”, scientists said it is not on the list of potential future Earth impact events.
Currently, the agency has identified 20,000 Near-Earth Objects. Of these, only a few are considered potential impactors, which NASA tracks via their automated Sentry System.
The near-miss 1998 OR2 might not pose a threat, but many scientists agree it’s only a matter of time before a huge asteroid collides with Earth.
Cardiff University scientist Ian McDonald told BBC Today, “Doomsday asteroid hits aren’t confined to the past. There are always rocks flying through space. One of these will hit us and it will have pretty dramatic effects.”
The last Earth impact was in 2013, and terrifyingly nobody saw it coming. Dubbed（被称为）the Chelyabinsk meteor, it exploded just 30 kilometers from Earth’s surface, shattering windows and rocking buildings for over 500 square kilometers, according to the BBC.
This impact injured around 950 people in Russia, but it just goes to show how precarious life on Earth is and how it could be devastated（毁坏的）by larger future impacts.
28. What can we learn about 1998 OR2?
A. It is as large as Mount Qomolangma.
B. It is heading for Earth at 3,908,791 mph.
C. It is likely to occur at the end of March.
D. It is estimated not to be a threat to Earth.
29. What would McDonald probably agree with?
A. There is little chance that the doomsday asteroid hits Earth.
B. A mega asteroid could unavoidably threaten Earth one day.
C. Potential impactors could be tracked and destroyed.
D. Mega asteroids could collide with Earth more often in the future.
30. By mentioning the Chelyabinsk meteor in the text, the author intends to________.
A. compare it with the upcoming 1998 OR2
B. present the dramatic effects of Earth impacts
C. show how frequent Earth impacts are
D. prove that little can be done in the face of an Earth impact
31. The underlined word “precarious” in the last paragraph probably means “_________”.
A. uncertain B. unprepared
C. precious D. diverse
【答案】28. D    29. B    30. B    31. A
【解析】