The correct Active/Passive form of the given sentence is:

☀ By whom is the class being disturbed?

So, the correct passive form is: "By whom is the class being disturbed?"

The other options and their explanations:

☀ The class is being disturbed by whom?

• This option is also in the passive voice and conveys the same meaning as the correct option. It is a valid passive construction, but the correct form uses a different word order for the question.

☀ The class are being disturbed by whom?

• This option is similar to the previous one but contains a subject-verb agreement error. The subject "the class" is singular, so the correct form should be "is being disturbed" instead of "are being disturbed."

☀ By whom are the class being disturbed?

• This option is a valid passive construction with a slightly different word order for the question. It conveys the same meaning as the correct option.