Step 1: Understand the task.
We must pick the sentence that is in correct passive voice. In passive voice, the subject receives the action.
Step 2: Recall the passive pattern.
A correct passive sentence needs the right helping verb plus the past participle of the main verb. If a helping verb is missing, the sentence is wrong.
Step 3: Check option A.
'Let the window be shut' uses the proper passive form for an order. 'Be shut' is the correct passive of 'shut'. So this one looks complete and right.
Step 4: Check the other options.
'What is said it?' is jumbled and ungrammatical. 'Ravi chosen leader of the group' is missing the helping verb 'was'. 'He will given the award' is missing 'be' and should read 'He will be given the award'.
Step 5: Compare the results.
Only option A has the full and correct passive structure. The rest are broken.
Step 6: State the conclusion.
The correct passive voice sentence is 'Let the window be shut.'
\[ \boxed{\text{Let the window be shut.}} \]