In the following questions, a sentence is given with a blank in it. It is then followed by five alternatives among which, one of the words fits correctly in the given blank so as to make the sentence meaningful. Find out the most suitable word and mark it as your answer.  The mission director exclaimed that the satellite's unexpected discovery of water vapor on the distant exoplanet was an _____________ achievement for modern astrophysics!

• Meaning of the sentence: The mission director declared that discovering water vapor on a distant exoplanet was a significant achievement in modern astrophysics. • Why Option A is correct: Exemplary means extremely good or outstanding. The discovery was an outstanding scientific achievement, making this the right fit. Why other options are wrong: • Ambiguous means unclear, which does not fit an achievement. • Elementary means basic or simple, which is unsuitable here. • Erratic means unpredictable or irregular, which does not fit an achievement. • Obsolete means outdated or no longer useful, which is unsuitable here.