He ________ (work) in the laboratory for three hours when he stopped for a break.
Alex ________ (read) a book all night and was very sleepy the next morning.
They were exhausted because they ________ (play) chess all day.
Before Fleming invented penicillin, he ________ (experiment) with bacteria for a long time.
I ________ (decide) that I was going to study Chemistry before I finished secondary school.
Alexander ________ (already/learn) to read and write before he started school.
He was upset because he ________ (miss) the last train.
He ________ (reach) his house by the time it started to rain.
Past Perfect/Past Perfect Continuous