________ he entered the classroom, he realized he had left his homework at home.
A.As B.Since C.If D.Until
The little boy was sleeping in the bed________ his mother was cooking in the kitchen.
A.since B.while C.because D.once
Jack has learned more about teamwork ________ he joined the soccer team.
A.until B.since C.while D.though
I like dancing, ________ I don't have enough time to practice it.
The train was late, ________ we had to wait for half an hour.
Study hard, ________ you may catch up with your classmates soon.
