BRUSSELS (AP) — Britain and the European Union have struck a free-trade agreement that should avert New Year’s chaos for cross-border commerce and bring a measure of certainty to businesses after years of Brexit turmoil. The breakthrough on Thursday came after months of tense and often testy negotiations that whittled differences down to three key issues: fair-competition rules, mechanisms for resolving future disputes and fishing rights. Now comes the race to approve and ratify the deal before the U.K. leaves the EU’s economic structures on Jan. 1. The British and European parliaments both must hold votes to ratify the agreement. And key aspects of the future relationship between the 27-nation bloc and its former member remain unresolved.