His pen has been stolen. (Active)

The correct answer is - ঘ) Someone has stolen his pen.

Passive থেকে Active voice-এ রূপান্তর:
- Passive-এর object (যদি থাকে) Active-এর subject হয়।
- Passive-এর subject Active-এর object হয়।
- Verb-এর tense ঠিক রেখে Active form ব্যবহার করতে হবে।

কোনো Passive Voice এ যদি object উহ্য থাকে (যা Active Voice-এ subject হওয়া উচিত), তবে Passive Voice-এর অর্থ অনুযায়ী যথোপযুক্ত subject বসাতে হয়।

Examples:
1. Passive: His pen has been stolen.
Active: Someone has stolen his pen.

2. Passive: He was murdered at day light.
Active: Someone murdered him at day light.

3. Passive: English is spoken all over the world.
Active: People speak English all over the world.

4. Passive: I had been invited to the party.
Active: My friend invited me to the party.

Other options
ক) His pen was stolen by him.
- এটি passive voice, tense ভুল (past simple)।
খ) They stole his pen.
- Tense ভুল (past simple)।
গ) A thief has been stolen his pen.
Grammar ভুল, has been stolen + subject → ঠিক নয়।

Source: Advance Learner's Communicative English Grammar & Composition by Chowdhury & Hossain.