Review of Passive Voice with Reporting Verbs. Have Something Done

Some other examples:

• It is known that the sky is blue / The sky is known to be blue
• It was thought that the Earth is flat   / The Earth was thought to be flat
• It was believed that Christopher Colombus was Galician. / C C was believed to have been Galician
• It is considered that space investigation will solve future health problems  / Space investigation is considered to solve future health problems.

Note: You have to pay attention to the tense of the "It + verb" part of the sentence AND the tense of the second part of the sentence. 

After studying the different options for passive voice, take some practice with these tests.