Toll(过路费)是由国家人为免收的,因此A. has cancelled 不在选择之列。句中没有表示早于cancell 的过去时间状语,不存在过去完成时D. hadbeencancelled。前面的reduce the increasing prices of vegetables(降低日渐高涨的菜价)是当前的举措,后面的if truck carrying them pass through a toll station(如果车辆运载蔬菜通过收费站)是也应该当前的条件,等于从句if truck carries them pass through a toll station。基于此,免收过路费是现行规定,因此应该用一般现在时B...