Question

It is known to all.(change the voice)

Answer 1

everyone knows it.....

Answer 2

Everyone knows about it.

Explanation:

The sentence is in the passive voice. It can be identified by the tense of verb in the sentence 'is known'. To change it into active voice, object becomes subject. In this case, 'all' cannot be the subject of the sentence. Therefore, a proper noun should be supplied if it is not present in  original sentence.

Therefore, by replacing 'all' with 'everyone', and changing the tense of the verb, the sentence becomes,  Everyone knows about it.