both sides accept the agreement will a lasting peace be established in this region.A. If o

问题补充：

both sides accept the agreement will a lasting peace be established in this region.

A. If only

B. Only if

C. unless

D. As long as

答案：

A. If only

(答案→)B. Only if

C. unless

D. As long as

解析：考查only的部分倒装句。Only倒装满足两个条件，only放在了句首，且强调的是状语，后面的主句使用部分倒装的形式。本题only放在了句首，强调的是条件句if both sides accept the agreement，后面的主句使用了部分倒装的形式。