The correct answer is A) A United States History textbook.
A primary source is one that was created at the time of the event(s) being discussed. Based on this information you can see that options B-D were all primary sources, as they were created during the time where the event was actually happening.
On the other hand, the US history textbook was created a long time after many of the events being discussed. This is why the textbook is considered a secondary source.