汉武帝时开始对匈奴进行大规模的反击，派兵从匈奴手中夺取了哪一地区[ ]

A．河套地区

B．河西走廊地区

C．漠北地区

D．河套和河西走廊地区

__________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