Why are subjective accounts often biased? a because subjective accounts are opinionated and emotional the narrator usually provides only on side of the story. b because subjective accounts are factual and impartial the narrator gives his or her opinion in indirect nuanced ways. c because subjective accounts are formal and academic the narrator can better emphasize the account irony and sarcasm d. because subjective accounts make heave use of imagery the narrator uses the setting to convey his or her outlook.

The answer is: [A]: Because subjective accounts are often opinionated and emotional, the narrator provides only ONE {added note: should read: "one"—not: "on"} side of the story.

Answer choice "B" is incorrect.  "Subjective accounts" are not both "factual and impartial"; and definitely not "impartial". Furthermore, given an "opinion" in "indirect, nuanced ways" is not a REASON [note the word: "because" in this answer choice] that an account would be "factual and impartial".  This answer choice would be inherently contradictory.  Furthermore, examine the question: "Why are subjective accounts often biased?".  The word "impartial" means "unbiased", so this answer choice would not make sense.

Let's look at Answer choice "C":  "because subjective accounts are formal and academic".  Subjective accounts may be "academic" —but not the most "formal".  Also, looked at the question:  "Why are subjective accounts often biased?"  It wouldn't make sense that the REASON an account would be BIASED is that an account is BOTH formal and academic."
 
But let's examine the final answer choice, "D: Because subjective accounts make heave {sic} [note: this should read: "heavy"] use of imagery the narrator uses the setting to convey his or her outlook."  This is not a reason why subjective accounts are often biased.  Furthermore, subjective accounts do NOT necessarily make heavy use of, or necessarily ANY use of, imagery.

It is clear that answer choice "A" is the best answer and the correct answer.

Because the vietnam war was fought in an especially brutal and untraditional way