What is the best example of a secondary source document useful in the study of history

The information box says that the han added 4,000 miles of wall. refer to the mileage scale. how can this be true?

Gretchen opens a high-end bakery in a busy section of town. customers pay top dollar for her quality baked goods. just two months later, emily opens a bakery across the street. she also sells baked goods but uses lower- quality ingredients and has a less appealing shop. some of gretchen's customers take their business to emily's bakery because her prices are lower. which industrial revolution-era system or movement is reflected in this scenario? o a. romanticism o b. marxism o c. social criticism o d. capitalism

The main reason the us senate rejected the treaty of versailles was because, isolationists felt the us should not have gotten into the war. republicans had gained power in the senate. democrats had gained power in the senate. european nations wanted to punish germany.