Why did she roll her eyes?
Because ...
Why did he make a funny face?
Because the singing was bad. / Because of the singer / contestant.
Why is he laughing?
Because ...
Why was he playing the trumpet?
Because ...
Why is he saying, "Thank you"?
Because ...
Why did he laugh?
Because his friend said something funny / Because of a joke.
Why was he crying?
Because ...
Why did he put his head in his hands?
Because they lost. / Because of a goal.
Why was he happy?
Because ...
Why was he sleepy?
Because ...
Why did he blow kisses?
Because ...
Why did he stop smiling?
Because ...
Why is he celebating?
Because ...
Why did he miss the train?
Because ...
Why is the teacher angry?
Because ...
Why is she waving?
Because of the people. / Because people are waving to her.
Why did he get angry?
Because ...
Why is she angry?
Because ...