The boy stood his head down, listening to his mother scolding him for breaking the windows.
It is _____ he often fails in exams _____ makes his parents worried about him.
Waves of red light are about twice as long as _______ of blue light.
Eventually, the husband could no longer ______ his wife’s complaints about his inability to make much money, and he divorced her.
Every year, _____ energy is spent on environment protection.
It is reported that the number of students_______ computer games has been on the increase in recent years.