Answer:
"As more people and businesses moved in, they needed buildings for living and working. They needed ways to move around the city."
Step-by-step explanation:
If you read the third paragraph the author already is developing in the text the explanation about the reasons about what were the immigrants doing during the expansion process, they were working, industries goes very well, families were getting bigger and they need to move and settle down. So if we removed that sentence the idea is the same and the author's explnation and objetive still being clear even, the conclusion does not change, you can read it again without that sentence and you will notice.