The correct option that expresses the given sentence in passive voice is:

☀ He was laughed at by all his friends.

So, the correct passive form is: "He was laughed at by all his friends."

The other options and their explanations:

☀ He became laughable to his friends.

• This option does not represent the same meaning as the original sentence. It indicates that "he" became someone or something that could be laughed at by his friends, rather than them actually laughing at him.

☀ His friends were being laughed at by him.

• This option reverses the subject and object of the sentence, making "his friends" the recipients of the laughter and "him" the one who is laughing at them. This does not match the meaning of the original sentence.

☀ All his friends were laughing at him.

• This option keeps the same meaning as the original sentence but does not use the passive voice. Instead, it is in the active voice with "his friends" as the subject and "laughing at him" as the action.