Answer: (already in the question)
Step-by-step explanation:
Reading about the thoughts and feelings of Abraham Lincoln during the Civil War is Primary source. This is because a primary source is coming from the person within the time period itself, meaning a dairy is an exmaple for this. The best place to find someone's thoughts and feelings is a dairy too.
Using a secondary source to read about the impact George Washingtpon had on US politics is the best choice. When George Washington became president, there were still loyalist parties. This means if you read a loyalist's diary when George Washington was president, there would be bias included. Another example is that the question would have been refering to future/ long term impact, so its best to read a source from present time.