21. He decided not to attend her birthday party________he had been invited to.
—What do you think of his speech at the court? —Er..., sorry, I ________ about something else.
We still remember once _________ round the famous tower when we were young.
----Marx looks nervous. ----So __________ you if you had so fierce a competition.
_________ caused the accident is still a mystery.
The sun began to rise in the sky, ________ the mountain in golden light.