Passage V

Aurora Mysterialis

[1]

The greatest light shows on Earth aren't fireworks displays (61) but rather the aurora borealis and aurora australis, also known as the northern lights and southern lights. These dazzling phenomena of shimmering colored lights, can be seen best near either polar region, their beauty stretching six hundred miles into the air.

[2]

While legends about the lights abound, sometimes these old tales conflict with one another. For years, many people thought the lights were a form of reflected sunlight. Then, in 1899, Norwegian physicist Kristian Birkeland led a dangerous winter expedition to the Arctic Circle to observe the lights. Upon his return the following year, he became the first scientist to advance a comprehensive explanation of why auroras exist.

[3]

Birkeland posited that the lights are the result of electrically charged particles from the Sun interacting with Earth's magnetic field. While most of the particles streaming past Earth are deflected by its magnetic field, some follow the field lines toward the poles, producing light as they collide with oxygen and nitrogen in the atmosphere.

[4]

Further research has refined Birkeland's theory regarding the magnificent light show. Auroral studies by spacecraft have confirmed the close link between sunspot activity and the lights. They have also shown how the electrons that cause the northern and southern auroras create simultaneous—often mirror-image—light shows, one at each pole.

[5]

Many of the era's top scientists ridiculed Birkeland's work, who scoffed at the notion that electrons from the Sun could reach Earth's magnetic field from such a great distance. However, it wasn't until the 1960s, when satellites first proved the existence of a ”solar wind“ of particles sweeping past Earth, that Birkeland's central tenet was substantiated.

[6]

Though we now have a clearer picture of why the lights occur, it remains incomplete. Even as new findings emerge while no scientific explanation can fully capture the lights' silent majesty. (74)

65. Which choice makes clear that Birkeland returned from the Arctic Circle in the year 1900?

Answer and Explanation

Your Answer is

Correct Answer is A

Explanation

To express exactly that he returned to the Arctic Circle in 1900, 1899 was mentioned earlier,

Item A: Upon his return the following year, the following year is modified as his return, so it can be judged His return took place the following year (i.e. 1990).

Item B: "the following year" is a modification of the sentence, so the specific time of his return cannot be judged.

Item C/D: that year refers to unknown.