A new security system was installed. ________, extra guards were hired.
A.As a resultB.Apart fromC.In that caseD.In addition在线课程D
解析：
题意：一个新的安全体系已经设置好了。另外还雇用了额外的门卫。in addition意为"另外"，符合题意。as a result"结果"；
apart from"除了"；
in that case"如果是那样的话"。