The employees _____more enthusiastic about their work since thei

The employees _____more enthusiastic about their work since their pay rose.
A、are
B、have been
C、were
D、will be
【正确答案】：B
【题目解析】：考查时态。句意：自从涨了工资，员工们工作起来更有热情了。since表示“自……”出现在句中时，主句要用完成时，故选B。