Questions 21-30 refer to the following passage.
We believe the Earth is about 4.6 billion years old. At percent we are forced to look to other bodies in the solar system for hints as to what the early history of the Earth was like. Studies of our moon, Mercury, Mars, and the large satelites of Jupiter and Saturn have provided ample evidence that all these large celestial bodies had formed. This same bombardment must have affected Earth as well. The lunar record indicates that the rate of impacts decreased to its present low level about 4 billion years ago. On Earth, subsequent erosion and crustal motions have obliterated the craters that must have formed during this epoch.
Scientists estimate the Earth’s age by measuring the ratios of various radioactive elements in rocks. The oldest Earth’s rocks tested thus far are about 3 1/3 billion years old. But no one knows whether these are oldest rocks on Earth. Tests on rocks form the moon and on meteorites show that these are about 4.6 billion years old. Scientists believe that this is the true age of the solar system and probably the true age of the Earth.
21. In line 8, the word “obliterated” means
(A) created
(B) destroyed
(C) changed
(D) eroded
Jawaban : (B) destroyed
22. According to this passage, how do scientists estimate the age of the Earth?
(A) By measuring the ratios of radioactive elements in rocks
(B) By examining fossils
(C) By studying sunspots
(D) By examining volcanic activity
Jawaban : (A) By measuring the ratios of radioactive elements in rocks
23. Scientists estimate the age of the Earth as …
(A) 3 1/3 billion years old.
(B) 4 billion years old.
(C) 4.6 billion years old.
(D) 6 billion years old.
Jawaban : (C) 4.6 billion years old.
24. Which of the following processes led to the obliteration of the craters formed by the bombardment of the Earth by the celestial bodies?
(A) Volcanic activity
(B) Solar radiation
(C) Gravity
(D) Crustal motions
Jawaban : (D) Crustal motions
25. According to the passage, why are scientists forced to look at other bodies in the solar system to determine the early history of the Earth?
(A) Human alteration of the Earth
(B) Erosion and crustal motions
(C) Solar flares
(D) Deforestation
Jawaban : (B) Erosion and crustal motions
26. What is the BEST title for this passage?
(A) “Determining the Age of the Earth”
(B) “Determining the Age of the Solar System”
(C) “Erosion and Crustal Motion of Earth”
(D) “Radioactive Elements in Rocks”
Jawaban : (A) “Determining the Age of the Earth”
27. Which of the following bodies was NOT studied to give evidence that the Earth was bombarded in its early history?
(A) Mars
(B) Mercury
(C) Jupiter
(D) Earth’s moon
Jawaban : (C) Jupiter
28. Bombardment of the Earth at one time by various sized bodies is
(A) inferred from what happened on other planetary bodies.
(B) documented fact.
(C) proven by the lunar record.
(D) indicated by erosion.
Jawaban : (A) inferred from what happened on other planetary bodies.
29. The level of impacts of the bombardments of Earth have
(A) decreased to below normal.
(B) increased to a current high.
(C)increased after a periodic low.
(D) decreased to a current low.
Jawaban : (D) decreased to a current low.
30. In line 6, the word “bombardment” means
(A) an avoidance.
(B) an assault.
(C) an effect.
(D) a cause.
Jawaban : (B) an assault.
