1. 题干：examples of different ways in which the parallax principle has been applied. (C9-T2-P2, T14)
原文：The parallax principle can be extended to measure the distances to the stars.
同义替换：
Different ways...applied --- be extended to
2. 题干：a description of an event which prevented a transit observation. (C9-T2-R2 T15)
原文：Fleeing on a French warship crossing the Indian Ocean, Le Gentil saw a wonderful transit-but the ship’s pitching and rolling ruled out any attempt at making accurate observations
同义替换：
Fleeing on a French warship crossing the Indian Ocean --- an event
Prevent --- rule out any attempt
3. 题干：a statement about potential future discoveries leading on from transit observations. (C9-T2-P2 T16)
原文：But such transits have paved the way for what might prove-to be one of the most vital breakthroughs in the cosmos-detecting Earth-sized planets orbiting other stars.
同义替换：
Potential --- pave the way
Discoveries --- breakthroughs
4. 题干：a description of physical states connected with Venus which early astronomical instruments failed to overcome (C9-T2-P2, T17)
原文：While the early transit timings were as precise as instruments would allow, the measurements were dogged by the ‘black drop’ effect.
同义替换：
Failed to overcome --- were dogged by
5. 题干：He calculated the distance of the Sun from the Earth based on observations of Venus with a fair degree of accuracy. (C9-T2-P2, T18)
原文：Johann Franz Encke, Director of the Berlin Observatory, finally determined a value for the AU based on all these parallax measurements: 153,340,000 km. Reasonably accurate for the time, that is quite close to today’s value of 149,597,870 km, determined by radar, which has now superseded transits and all other methods in accuracy.
同义替换：
Fair degree of accuracy --- Reasonably accurate
Calculated --- determined
The distance of the Sun from the Earth --- a value for the AU
6. He understood that the distance of the Sun from the Earth could be worked out by comparing observations of a transit. (C9-T2-P2, T19)
原文：He realised that, from different latitudes, the passage of the planet across the Sun’s disc would appear to differ.
同义替换：
Comparing observations --- different latitudes
7. He realised that the time taken by a planet to go round the Sun depends on its distance from the Sun. (C9-T2-P2, T20)
原文：Johannes Kepler, in the early 17th century, had shown that the distances of the planets from the Sun governed their orbital speeds, which were easily measurable.
同义替换：
The time taken by a planet to go round the Sun --- orbital speeds
Depends on --- govern
8. He witnessed a Venus transit but was unable to make any calculations. (C9-T2-P2, T21)
原文：Fleeing on a French warship crossing the Indian Ocean, Le Gentil saw a wonderful transit-but the ship’s pitching and rolling ruled out any attempt at making accurate observations.
同义替换：
Witnessed --- saw
Was unable to --- ruled out
9. Halley observed one transit of the planet Venus. (C9-T2-P2, T22)
原文：Nevertheless, he accurately predicted that Venus would cross the face of the Sun in both 1761 and 1769-though he didn’t survive to see either.
同义替换：
Observed --- see
Transit of the planet Venus --- Venus would cross the face of the Sun
10. Le Gentil managed to observe a second Venus transit. (C9-T2-P2, T23)
原文：Ironically after travelling nearly 50,000 kilometers, his view was clouded out at the last moment, a very dispiriting experience.
同义替换：
Managed to observe --- his view was clouded out
11. The shape of Venus appears distorted when it starts to pass in front of the Sun.(C9-T2-P2, T24)
原文：When Venus begins to cross the Sun’s disc, it looks smeared not circular-which makes it difficult to establish timings.
同义替换：
Appears --- looks
Distorted --- not circular
Starts --- begins to
Pass in front of the Sun --- cross the Sun’s disc
12. Early astronomers suspected that the atmosphere on Venus was toxic. (C9-T2-P2, T25)
原文：While this showed astronomers that Venus was surrounded by a thick layer of gases refracting sunlight around it, both effects made it impossible to obtain accurate timings.
同义替换：
Atmosphere --- gases
13. The parallax principle allows astronomers to work out how far away distant stars are from the Earth. (C9-T2-P2, T26)
原文：The parallax principle can be extended to measure the distances to the stars.
同义替换：
Work out --- measure
How far away --- the distances
