Correct Answer: obsolete

Solution : The correct choice is the f irst option: obsolete.

Defunct refers to something that is no longer in existence, operation, or use.

Obsolete refers to something outdated and no longer in use due to advancements or changes in technology, practice, or understanding, and is the synonym for "defunct".

The meanings of the other options are as follows:

• Ancient: It describes something that belongs to the past, typically a period in human history.
• Contemporary: It pertains to something that exists or occurs at the same time as the current period.
• Prominent: It describes someone or something important, famous, or well-known.

Therefore, the correct sentence is: "The ruins of this building do tell us the story of an obsolete organisation."