问题
选择题
—You were out when I dropped in at your house.
—Oh,I for a friend from England at the airport.
A．was waiting
B．had waited
C．am waiting
D．have waited
答案
答案：A
过去进行时可表示过去某一时间正在进行的动作或存在的状态。答语中暗含了when you dropped in at my house。