The correct active voice form of the given sentence "All weapons were surrendered by them" is They surrendered all weapons.

The passive voice of the sentence is "All weapons were surrendered by them." This sentence is in the simple past passive voice, which is used to describe an action that happened in the past. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the past participle of the main verb. In this case, the subject of the active sentence is "weapons" and the main verb is "surrender." The past participle of "surrender" is "surrendered." So, the passive form of the sentence is "All weapons were surrendered by them."

The active voice of the sentence is formed by putting the subject of the passive sentence before the verb and removing the word "by." In this case, the subject of the passive sentence is "them," and the verb is "surrender." So, the active form of the sentence is "They surrendered all weapons."

The other options are incorrect because:

• They have surrendered all weapons." This sentence is in the present perfect active voice, which is used to describe an action that has happened in the past and is still relevant to the present. However, the action of surrendering the weapons has not happened yet.
• They had surrendered all weapons." This sentence is in the past perfect active voice, which is used to describe an action that happened in the past before another action happened. However, there is no other action mentioned in the sentence.
• They are surrendering all weapons." This sentence is in the present progressive active voice, which is used to describe an action that is happening now but is not finished. However, the action of surrendering the weapons is not happening now.