SAT阅读官方每日一练（附答案和解析）2018.8.23

Light from distant quasars—early galaxies that shine with tremendous brightness—has given researchers anew clue to the origin of vast magnetic fields studding today's galaxies: They were running strong when the universe was only a third of its percentage.

Astronomers had observed that radio emissions from quasars tend to be angled, or polarized, in such a way that powerful magnetic fields must have twisted them. The greater their distancefrom Earth, the more polarized their light. But researchers didn't know whether the magnetic fields were part of the quasar or were present in galaxies encountered by quasar light as it made its journey to our telescopes.

So a team led by astronomers from the Swiss Federal Institute of Technology (ETH Zurich)scanned more than 70 of those quasars using the European Southern Observatory's Very Large Telescope in Chile to look for signs of galaxies hiding in front of the quasars. Specifically, theychecked for a feature called the magnesium(II) absorption line, a reduction in the intensityof light of a certain wavelength, which is a commonly used indicator that gas from a star-forming galaxy has soaked up that light.

The researchers report that light from quasars showing the magnesium(II) line was morestrongly polarized than light from other quasars in the sample. The interpretation: that light did indeed pass through regular galaxies and that it likely acquired its polarization in the process.

They estimated the age of the magnetic galaxies by measuring the red shift of theabsorption line—the observed reddening of light that occurs when galaxies move rapidly apart.The typical red shift of the inferred galaxies corresponded to an age of 5.2 billion years, studyauthor Francesco Miniati says. Precision measurements of the cosmic microwave backgroundpeg today's universe at 13.7 billion years old.

According to the passage, the astronomers wanted to determine if light emitted bydistant quasars was affected by ____________

A.the number of stars in those quasars.

B.those quasars' proximity to galaxies.

C.the age of those quasars.

D.those quasars' distances from Earth.

重点单词：

wavelength ['weiv.leŋθ] n. 波长，波段

interpretation [in.tə:pri'teiʃən] n. 解释，阐释，翻译，(艺术的)演绎

determine [di'tə:min] v. 决定，决心，确定，测定

critical ['kritikəl] adj. 批评的，决定性的，危险的，挑剔的

institute ['institju:t] n. 学会，学院，协会vt. 创立，开始，制

precision [pri'siʒən] n. 精确，精密度adj. 以精准的执行而著

sample ['sæmpl] n. 样品，样本vt. 采样，取样

reduction [ri'dʌkʃən] n. 减少，缩小，(化学)还原反应，(数学)约分

proximity [prɔk'simiti] n. 接近，亲近

soaked [səukt] adj. 湿透的 动词soak的过去式和过去分词

答案：B

解析：

Choice B is the best answer. The passage states that the astronomers used the European Southern Observatory's Very Large Telescope to see if galaxies were "hiding in front of the quasars" and checked to see if gas from those galaxies had "soaked up" those quasars' light. In other words, the astronomers were investigating the effect galaxies near quasars had on the quasars' light.