You are under 18 years old, so it’s _______for you to join Trail walker.
He could play the violin when he was five.
The students ought to wear school uniforms when they’re at school.
Mr. Green is very happy because he is satisfied with his students’ work today.
_______ the teachers in their school is about 200 and one fourth of them are _______ teachers.
He didn’t go to school yesterday ________ he was ill.