遅れたわけを説明してもらいたい。

to be late; to be delayed; to fall behind schedule; to be overdue

conclusion from reasoning, judgement or calculation based on something read or heard; reason; cause; meaning; circumstances; situation

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

explanation; exposition