The correct answer is D) objective.
The other options of the question were A) biased. B) colorful. C) obvious.
When a writer is trying to explain or inform it is likely that the point of view will be objective.
This is very important because the writer knows that people who read ts text is going to consider the information as true. So it is a great responsibility for the writer to always maintain the objectivity of its explanation, ideas or arguments. He/she knows that valid sources are needed to support the information and his explanation. The author would never bias the explanation or be judgmental.