You can go out you promise to be back before 10 o’clock.A. unlessB. as long asC. becauseD.

问题补充：

You can go out,you promise to be back before 10 o’clock.

A. unless

B. as long as

C. because

D. since

答案：

A. unless

(答案→)B. as long as

C. because

D. since

解析：连词辨析。A除非，如果…不；B只要；C因为；D自从，既然；句意：只要你答应10点之前回来，你可以出去玩。故B正确。