学校的路灯经常烧坏，更换十分不便，电工师傅用“挑担灯’’解决了这个问题，即将“220V 100W”和“220V 60W”的甲乙两盏规格相同的白炽灯串联接入照明电路．上述两盏灯相比较，灯丝较粗的是______灯，两灯工作时，较亮的是______灯．（填“甲”或“乙”）

--Mum, it's late. Why are you still here?

--Dad hasn't come back yet. I          for him.

A. am waiting                B. was waiting                 C. waited