Answrs: Part a) "Facts from a documentary.." This is talking about the benefits of artificial organs instead of donated ones.
Part b) "There are several ..." Because it is a sentence that is likely to precede facts. The others are opinions about how something 'SHOULD' be, and aren't presenting facts or claiming something.The first one 3ven says "I think..." which is clearly an opinion.
The best time to determine voice & tone in writing is when you are in the beginning/middle of the passage/book/article because you will see what the author is going to talk about and then how he feels about it.
Troy Davis was not allowed to submit to the lie detector to prove his guilt before being executed, as a last resort to avoid lethal injection. His defenders accused the Court of racial discrimination.
Davis´s attorney, Stephen Marsh, has commented that the Georgia department of corrections rejected the request to take the polygraph test. However, until the last minute Davis, did not recognize himself guilty of the murder of police officer Mark McPhail in 1989.
In spite of the doubts about the sentence, lack of real evidence of Davis´s participation in that murder and numerous social protests, the supreme court of the United States rejected the last request of clemency.
In both cases we can infer, although the country fights in order to defeat the racism, is a currently present problem.
"Today nobody brought his or her instrument" is correct. It is common for people to use "their" in a sentence like this, but "his or her" is the more proper term.
