Exercise 1: Fill in the blanks with "Because" or "Because of" She was tired ______________ she walked so long. He walked out in the middle of the film ______________it was so long and boring. We had to hurry indoors ______________it was raining. I am late ______________the traffic. They stayed at home ______________the rain. Nick is often punished ______________he is lazy. I couldn't go to the cinema ______________the heavy rain. Schools teach mathematics ______________its importance.