Which of the following sentences contains at least one error? a. Campaigning heated up in the swing states as the election approached, with both sides making a last bid for the independent vote. b. The new department manager's practices, from closed-door meetings to ultimatums and disastrous snap decisions, quickly alienated the staff. c. The workers threatened a strike once it became clear that the company was unlikely to accept their demands. d. Critics complain that the school board's new policy merely introduces miner modifications and does nothing to amend the real faults in the system