________ energy is generated from natural resources—such as sunlight, wind, rain, tides and so on.
In my opinion, life in the twenty-first century is much easier than ___________.
The field research will take Joan and Paul about five months; it will be a long time _________ we meet them again.
— I phoned you yesterday morning. A girl answered, but I didn’t recognize the voice.— Oh, it __________ my younger sister. She was in my room at that moment.
He _______ Alice for ten years.
He hesitated for a moment before kicking the ball, otherwise he ______ a goal.