Select the most appropriate option to fill in the blank no. 6.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. the.
The passage talks about the castles and their relation to history as they tell us about historical details of ancient times.
The sentence talks about messages being conveyed through floorboards etc.
So the article "the" should be used as it is followed by the noun the upper chambers.