一个四棱锥和一个三棱锥恰好可以拼接成一个三棱柱.这个四棱锥的底面为正方形,且底面边长与各侧棱长相等,这个三棱锥的底面边长与各侧棱长也都相等.设四棱锥、三棱锥、三棱柱的高分别为,,,则( )
Smoking, ______ is a bad habit, is popular with the young.
The number of the people who own cars ______since 1990.
— Is he coming? — ______. He may not have time.
It took him a long time to ______ the skills he needed to become an artist.
There is no doubt ______ he did is good for us.