一道英语题,求解aWhen I--(open)the door.I--(see)a man on his kness .

一道英语题,求解a
When I--(open)the door.I--(see)a man on his kness .He clearly --(lisen) to our conversation and I--(wonder) how much he --9hear).When I--(ask) him what he --(do),he --say that he--(drop) a 50p piece outside the door and --(find) for it .I --(not see )any sign of the money but I--(find) a small notebook and a pencril which he probably --(drop)when the door--(open)suddenly.