Some time ago, an interesting discovery __ by archaeologists on the Aegean Island of Kec.a.has been madeb.is madec.had to be maded.was made

The correct choice for filling in the blank is d. was made.

Here's the reasoning:

1. Grammar Structure: The sentence requires the past simple passive form, as it refers to a discovery that has already occurred.
2. Options Analysis:
   • a. "has been made" suggests a connection to the present, which doesn't fit with the past context.
   • b. "is made" implies a present tense, which is also incorrect for this context.
   • c. "had to be made" suggests necessity rather than simply stating that the action happened.
   • d. "was made" properly indicates that the discovery occurred in the past without unnecessary implications.

Thus, the complete sentence reads: "Some time ago, an interesting discovery was made by archaeologists on the Aegean Island of Kec."