부사절 풀이 다잡아 (4)

[11~12] 다음 글을 읽고, 물음에 답하시오.

 For nearly a half-century, starting in 1949, the world’s most powerful research telescope was the Hale, on Palomar Mountain, in California. Its mirror, 5 m in diameter, focused more faint starlight than anything else on the planet. Impressive as the Hale telescope was for its day, it came to a technological ___(A)___. In the past years, the Hale has been humbled. With a mirror more than 8 m in diameter, the twin Gemini telescopes in Hawaii and Chile provide almost complete coverage of both the northern and southern skies. And the twin Keck telescopes, whose light-gathering surfaces are an astonishing 10 m in diameter, boast scopes more powerful than anything else. While each of these instruments trumps the Hale in light-gathering power, many are poised to outshine even the Hubble Space Telescope. Using an ingenious technological trick to eliminate atmospheric blur, most of the telescopes will achieve Hubble-quality focus and even beat it under the right conditions. This is a    (B)    of astronomical proportions.