D. To leave unanswered questions for the audience to think about
The questions leave the audience to come up with their own answers. However, the way the questions are asked he is guiding the audience to have similar answers. If we look at the other options, it is almost easier to eliminate the other options to verify that we are correct. Option A talks about a warm comfortable feeling. However, Wiesel does not want to leave the audience feeling warm and comfortable. He wants the audience to have a reaction to the horrors and injustices being done in the world. He no longer wants people to be indifferent to human suffering. Option B mentions are religious plea...there is no religion in his questions. Option C is about him directly stating his opinion. Questions are not direct statements...this is wrong. Option D is the only valid choice.
The prepositional phrase for this sentence is "go until Friday." The word "go" is a preposition. Think of it as a squirrel and a log. To find a preposition, say "The squirrel (went) [insert preposition] the log." If it makes sense, it is a preposition. Then just find the phrase to go along with it!
If the words brave and courageous were used in the same context, they would be examples of <span>C. synonyms.
</span>Synonyms are words that have the same meaning. Antonyms are words that have the opposite meanings. Brave and courageous are adjectives, so they cannot be either A or D.