A sentence has been given in Active/Passive voice. Out of the four alternatives suggested below, select the one which best expresses the same sentence in Passive/Active voice. 
 

All his classmates laughed at him. 

He was laughed at by all his classmates.

He was laughed at by all his classmates.

Explanation:

• He was laughed at by all his classmates.: This passive construction correctly reverses the subject and object, forming the passive voice while maintaining the original meaning.
• He was laughed by all his classmates.: This passive construction has the correct subject and object reversal but is missing the preposition "at," which is necessary to maintain the original meaning.
• He was being laughed by all his classmates.: This passive construction is grammatically incorrect, as it should be "being laughed at" to correctly form the passive voice.
• He was being laughed at by all his classmates.: This passive construction correctly reverses the subject and object and uses the correct preposition "at" to form the passive voice.