The boy felt really upset because

The boy felt really upset because he was late.

The boy felt really upset because he had missed his train.

The boy felt really upset because it was raining.

The boy felt really upset because he was alone.

The boy felt really upset because he had got a bad mark.

The boy felt really upset because he had missed her letter.

The boy felt really upset because he couldn’t find the house.

The boy felt really upset because he had forgotten his name.

The boy felt really upset because had lost his wallet.