问题

You will find the game is not so difficult to play ______ you understand its rules.
A:until
B:since
C:before
D:once
B:since
C:before
D:once
正确答案是:
同类题型
China has became the third nation to send aperson into space______________.
_______ over a week ago, the books are expected to arrive any time now.
You have no chance of getting the position I’m afraidyou _____ your time if you apply for it
__ we ________ the other road, we might have arrived here in time for the meeting.