Another term for a through line is

Which of the following scientific advancements did NOT occur between 1830 and 1871?

A. Data were collected showing that modern plants and animals had evolved from simpler forms through a process of natural selection. B. The germ theory of disease was established. C. The interior structure of the atom was fully mapped out. D. Chloroform and other anesthetics were introduced.

The title of Grant Wood's American Gothic was inspired by _____.

Fill in the blank(s) with the appropriate word.