UPS工作中时常突然出现周期性声光告警，最常见的原因是（）。
A、UPS故障
B、负载设备故障
C、电池欠压
D、市电停电
参考答案：D
需与症状不典型的急性胰腺炎相鉴别的疾病有（）
A.肠梗阻
B.急性胃炎
C.消化性溃疡穿孔
D.胆石症
E.肾绞痛
Tom _____ the car for two months.[ ]
A. has had
B. bought
C. has bought
D. had got
