anonymous"The birds are flying in the sky" or "Birds are flying in the sky"Changes in passive voice
There is no transitive verb phrase in your example, so it cannot be passivised. Only transitive VPs can be passivised, compare Donald Campbell broke the land speed record in 'Bluebird . [active] The land speed record was broken by Donald Campbell in 'Bluebird '.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
There is no transitive verb phrase in your example, so it cannot be passivised.
Only transitive VPs can be passivised, compare
Donald Campbell broke the land speed record in 'Bluebird. [active]
The land speed record was broken by Donald Campbell in 'Bluebird'. [passive]