B.the one
变成肯定的:
the exhibition is () the foreign friends visited yesterday.
(the foreign friends visited yesterday.)这句显然是个定语从句部分.
没有先行词,
即:主句:the exhibition is()没有表语.
自然是B ,这个展览,就是(那个),外国友人们昨天参观的(那个)吗?the one ,正合意.