Answer:
The forgery was so exquisite that it hung in the museum for the past two decades without discovery.
Explanation:
We need to use context clues to choose the appropriate verb tense for this sentence. Notice how the sentence talks about the forgery in the past tense, saying it hung there for the past two decades. The best thing to do is to choose a verb that is also in the simple past tense, otherwise the two parts of the sentence will contradict each other. If we said something like "The forgery is being so exquisite that it hung etc.", it would sound off. Therefore, the best option is "The forgery was so exquisite that it hung in the museum for the past two decades without discovery."
