Choose the option that is the passive form of the sentence.

The detective found the lost necklace.

The lost necklace was found by the detective.

In the active voice sentence, "The detective found the lost necklace," the subject (detective) performs the action (found) on the object (the lost necklace).

To convert the sentence to passive voice, we make the object (the lost necklace) the subject of the sentence and use the past participle form of the verb "found" (was found). The agent or the doer of the action (the detective) is introduced with the preposition "by."

Therefore, the passive voice sentence is: "The lost necklace was found by the detective."

The other options are incorrect:

1. "The lost necklace should find the detective" is not in passive voice, but rather in active voice, and it changes the meaning of the sentence. In the original sentence, the detective is the one who performs the action of finding the necklace, not the other way around.

2. "The lost necklace founded by the detective" is not grammatically correct. The correct form would be "was founded" as the past participle of "found," and the preposition "by" should introduce the doer of the action.

3. "The lost necklace had been find by the detective" uses the wrong verb form. The past participle of "find" is "found," not "find," and the correct auxiliary verb in this case would be "had been."

Therefore, the correct option is: "The lost necklace was found by the detective."