In a life time a person (a)_____________ about a year looking for things they have lost. The things that people (b)____________ most frequently are umbrellas, keys, bags and mobile phones. Most public transports have a lost and found office, where objects that(c) ______________ behind on trains or in buses are kept until their owners (d)___________them. London’s lost property office deals with about 130,000 items a year.

i just want the answer for option c , whether it is have left behind or had left behind along with the reason for the same