Question

Which sentence does not contain any punctuation errors? A. Once we finished up our chores Mom began to assign more. B. Once we finished up our chores, Mom began to assign more. C. Once, we finished up our chores Mom began to assign more. D. Once we finished up, our chores, Mom began to assign more.

Answer 1

A, it's not it because you need a comma after chores.
B :)
C, No need for a comma after once.
D, no commas needed in between our chores.
Therefore your answer is B