Respuesta :
The thesis for this particular excerpt would be option A - In the 1800s, the United States was still a very young nation, trying to solidify its identity. A thesis is the statement that an author will put forward to be maintained, and from the available information from the question, it seems likely that this particular sentence will be the correct answer.
The sentence that serves as the author's thesis from the introduction paragraph is Yet key technological developments caused a rapid growth in American urban areas.
What point was the author trying to make?
The author was trying to draw attention to the fact that even tough the United States was a young nation which was late to the Industrial Revolution, it still experienced a rapid growth in urban areas.
The thesis statement would therefore be about the growth of American urban areas, as other statements included in the excerpt were garnered at supporting this on statement.
In conclusion, option D is correct.
Find out more on thesis statements at https://brainly.com/question/2094985.