Choose the correct synonym for the underlined word in the following s…

The correct answer is Option (1) → ambiguity

• Obscurity has two meanings: (1) the state of being unknown or not famous, and (2) the quality of being unclear or hard to understand. It comes from the Latin obscurus (dark). In the sentence, "working in obscurity" is set against "found recognition", so it is used in the first sense.
  Example: The poet lived in obscurity until his first book became a success.
• Ambiguity means the quality of having more than one possible meaning, being unclear. It is a synonym of obscurity in its second sense, and it is the only option that is a synonym of the word at all.
  Example: The ambiguity of the rule led to many disputes.

Why the Other Options are Incorrect?

Option 2: light — Incorrect. Light, in the sense of public attention (as in "come to light"), is nearer to the opposite of obscurity.
Example: The truth finally came to light.

Option 3: certainty — Incorrect. Certainty means the state of being sure; it is not related to being unknown, and it is the opposite of being unclear.
Example: We cannot say with certainty when the train will arrive.

Option 4: transparency — Incorrect. Transparency means openness and clearness; it is the opposite of obscurity in the sense of being unclear.
Example: The new rules bring more transparency to the selection process.

Note: In this sentence "obscurity" means being unknown, and no option gives that sense (a word such as "anonymity" would). Ambiguity is the answer because it is the only option that is a synonym of obscurity, in its sense of being unclear.