Question

Quasars, at billions of light-years from Earth the most distant observable objects in the universe, believed to be the cores of galaxies in an early stage of development.

• A. believed to be
• B. are believed to be
• C. some believe them to be
• D. some believe they are

Answer 1

The correct option is B are believed to be

B is the correct answer.

All of the others make incomplete sentences. Just take out the middle phrase, at billions of light-years from Earth the most distant observable objects in the universe, and read the sentence.to easily get the answer.