Question

Which sentence does not contain any punctuation errors? A. She always shuts the gate otherwise, the pig follows her out. B. She always shuts the gate, otherwise, the pig follows her out. C. She always shuts the gate, otherwise; the pig follows her out. D. She always shuts the gate; otherwise, the pig follows her out.

Answer 1

by sounding out the sentences b is the only that sounds right

Answer 2

If you say it and pause where you should so that it makes sense, only B is correct.  The comma after gate separates the two clauses. the comma after otherwise sets off this conjunction from the rest of the clause.