Step 1: Idea:
We will use the meaning of the Persian words and then confirm with the bracket meanings in the passage, checking each option.
Step 2: Break the word:
'Diwan' means a hall or court. 'Am' means common or public. 'Khas' means special or private.
Step 3: Match to the question:
A hall of selective audience means a hall for a chosen few. So it must be the Diwan with Khas, the special hall.
Step 4: Check the other options:
Diwan-i-Am is the public hall, Moti Masjid is a mosque and Hamam is a bath, none of which is a hall of selective audience.
Step 5: Confirm with the passage:
The passage puts the bracket 'hall of selective audience' right after Diwan-i-Khas, which agrees with Option 4.
Final Answer:
The special hall for selected guests is the Diwan-i-Khas, so the answer is Option 4. \[ \boxed{\text{Diwan-i-Khas}} \]
