Answer:
Treehouses can make special and unique houses. Treehouses are really hard to build and maintain.
Explanation:
<span>a heroic epic
HVE GREAT DAY </span>
A dash should be inserted after the word nanoscale
B, handwritten letters, because the letters are probably the most credible, especially since they're a first-hand account of things that happened to your ancestors, and as WorldlyGlass45 mentioned in their answer to this question on another post, you'll most likely get the most info from the letters as well.