Cars play an important role in modern life, but they_______also cause many problems like air pollution．

There were already five people in the car but they managed to take me as well . It ____ a comfortable journey . 

Among the 15-year-old children, some        studying in university while others are still learning to read and write.

— Why didn’t you go to the dance last night? — If I             tired, I would have.

He seldom listens to others. He＿＿＿＿＿answer for what he has done.