I'm almost sure that it's a
His friendship with ferdinand david
Answer: I appreciate you and your question. Just wanted to say thanks for you reaching out and I may not know you but you seem like a good human being.
Explanation: Have a good day.

TOPIC:- PASSIVE VOICE
QUESTION:- He was painting a portrait.
ANSWER:- A portrait was being painted by him
RULES FOR FORMATION:-
1. Change the object into subject.
2. use 3rd form of verb .
3. use by and then use subect as object.
HOPE IT HELPES YOU.