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

☀ Let the door be opened.

 Explanation for other options:

☀ You should open the door. This option is still in the active voice, but it changes the sentence into a suggestion or advice. It conveys a similar meaning but is not a passive form of the sentence.

☀ Let this door be opened. This option is also a passive construction, but it changes the meaning slightly by specifying "this door" instead of simply "the door."

☀ You are requested to open the door. This option is in the passive voice, but it includes the subject "you" and changes the structure to a request rather than a direct imperative command. While it conveys a similar meaning, it is not the same as the original sentence.