The correct answer is A) high-pressure water wash. A high-pressure water wash is an acceptable method for cleaning a dirty condenser coil in an air-cooled container refrigeration system. This method is effective at removing accumulated dirt and debris from the coil without causing damage to the delicate coil fins. The other options are not recommended, as B) a copper wire rotary brush could potentially damage the coil, and C) a 'Binks' gun with a weak acid solvent could potentially cause corrosion and damage to the coil material.