I don’t know if this will help
Development of more railroad systems contributed
most to US westward expansion in the second half of the nineteenth century.
The correct answer between all the choices given is the second choice or
letter B. I am hoping that this answer has satisfied your query and it will be
able to help you in your endeavor, and if you would like, feel free to ask
another question.
Do you have a picture of the page? Maybe I can help...
Answer:
It would be phytoplankton.
