The given sentence is in Active Voice. As per the given question we have to change it into Passive Voice.
The structure of the given sentence as follows:
Subject + V2+ Object. (Active Voice)
Subject (objective case)+ was/were + V3 + Object (subjective case). (Passive Voice)
Example:
Their cousin showed them some rare photographs. (Active Voice)
They were shown some rare photographs by their cousin. (Passive Voice).
The subject of the given sentence is 'All his friends'.
The object of the given sentence is 'him'.
The subject will be put in place of the object and the object will be put in place of the subject.
And 'laughed' will be changed into 'was laughed'. Lastly, the 'by' preposition will be added.
Therefore, as per the points mentioned above, we find that the correct answer is Option 2.

Detailed Solution
The correct answer is- The ending of the play surprised the audience.
Additional Information
The given sentence is in a passive voice form, hence we need to convert it into an active voice form.
Find the subject (The audience) and object (the ending of the play) of the sentence and exchange their places.
The given sentence is in the simple past tense.
The active verb form for simple past is: Subject + past participle form of the verb + Object.
So, 'was surprised' changes to 'surprised'. At last line up the remaining part.
Following these steps, we finally get- The ending of the play surprised the audience.