Question

you are researching space exploration. which would be the best source to use for your research? an online video about earth a social media post about space a book written by a scientist who studies space

Explanation:

A book written by a scientist who studies space is likely to be more reliable and in - depth. An online video about Earth may not focus on space exploration. A social media post may lack credibility and depth.

Answer:

a book written by a scientist who studies space