Помогите с английским , пожалуйста.

Change Passive sentence into Active one
The basic sentence is

Who invented the camera?


Who 1)______the camera 2) ______.

1)
was, were, has been, are ,is

2)
invented by, invent, invented

zorbing: Дискуссии с носителями дело, конечно, хорошее, но грамматики дают именно вариант 'Who ... by?' Цитата из 'OXFORD GUIDE TO ENGLISH GRAMMAR' by John Eastwood, p.135 - We use 'by' in a question about the agent. 'Who were the drugs found by?'