Select the option that expresses the given sentence in active voice.
All weapons were surrendered by them.

The correct option is "They surrendered all weapons."

To convert the sentence from passive voice to active voice, we can follow these step-by-step rules:

Step 1: Identify the components of the passive sentence
- Receiver of the action (Subject): "All weapons"
- Verb phrase: "were surrendered" (indicating simple past tense in passive form)
- Doer of the action (Agent): "them" (introduced by the preposition "by")

Step 2: Convert the agent into the active subject
The objective pronoun "them" becomes the subjective pronoun "They" when it acts as the subject of the active sentence.

Step 3: Convert the verb form
The passive verb "were surrendered" is in the simple past tense. In the active voice, the simple past tense of the verb "surrender" is simply "surrendered".

Step 4: Convert the passive subject into the active object
The noun phrase "all weapons" becomes the direct object receiving the action in the active sentence.

Step 5: Assemble the active sentence
Combining the subject, verb, and object gives:
"They" (Subject) + "surrendered" (Verb) + "all weapons" (Object) ⇒ "They surrendered all weapons."