400
Cottage industry, also (A) known as the putting-out system, was the initial phase of industrialization, (B) although it was soon overshadowed by other systems of production (C) that (D) have become widespread during the Industrial Revolution of the 19th century. (E) No error
(A) known: This is in a modifying phrase—an SAT favorite—so you should check that it’s next to the correct noun. “Cottage industry” is what’s known as the putting-out system, so there’s no problem.
(B) although: This linking word shows a contrast. Should there be one? Yep. Move on.
(C) that: What does “that” refer to? A place or time? Nope—it’s a thing (“systems of production”), so it’s fine.
(D) have become widespread: This is a verb, so you should check both the subject and the tense. The “systems” are plural, so “have” is correct in number (not “has”), but the time is wrong! It should say “became widespread.”
D