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

☀ The street dogs must not be harmed.

So, the correct passive form is: "The street dogs must not be harmed."

The other options and their explanations:

☀ The street dogs must not being harmed.

• This option contains a grammatical error. The correct form should be "be harmed" instead of "being harmed" to form the passive voice correctly.

☀ The street dogs must not have harmed.

• This option is in the active voice, not the passive voice. It uses the modal verb "must not" followed by the base form of the verb "have harmed," indicating that the street dogs are not allowed to cause harm, but it does not convey the passive voice.

☀ The street dogs might not be harmed.

• This option uses the modal verb "might not," which indicates possibility or permission, not prohibition. The original sentence uses "must not," which indicates prohibition or obligation. The correct option uses "must not," not "might not," to maintain the same meaning as the original sentence in the passive voice.