No one can tell the reason.
What was the cause of the explosion?
The cause of the fire was unknown.
This is why I came back.
How do you account for your absence?
Marriage is the main cause of all divorces.
The reason the cat is not included in the 12 animals of the Chinese zodiac is very simple.
The cause of the fire is not known.
Many flights were canceled, owing to the typhoon.
There are many good reasons not to do it.