Question

Which would be the least helpful for supporting interpretations about the lives of late nineteenth-century immigrants?

Answer 1

An early twentieth-century real estate ad promising "bliss"

Answer 2

 - -   an early twentieth-century real estate ad promising “bliss” 
This is because you do not need to know ad promising,

A journal entry, a historical novel, a factory's worker pay, and more all help you.

Unlike a ad. 

~Hope this helps