Which of these is a compound sentence?
1. immigrants who came to work in factories lived in urban neighborhoods.
2. “old” immigrants often settled on farms, but most “new” ones lived in cities.
3. in the past, many immigrants had come from northern and western europe.
4. immigrants working long hours and facing crowded living conditions.

The correct answer is 2. "Old" immigrants often settled on farms, but most "new" ones lived in cities

Explanation

A compound sentence is a sentence that has two independent clauses which mean each one has a subject, verb, and complement, and express a complete idea. Additionally, compound sentences are linked by a semicolon, comma or conjunction such as and, for, or, yet, so or but. In the case of the second option, there are two independent clauses (subject, verb, and complement) that express a complete idea, joined by the conjunction but.

"Old" immigrants (subject) often settled (verb) on farms (complement), but (conjunction) most "new" ones (subject) lived (Verb) in cities (complement)