The correct answer is A) The dew point is taken at the ventilation exhaust trunk. The dew point is measured at the ventilation exhaust trunk because this is the location where the air leaving the cargo hold is sampled. By measuring the dew point at the exhaust, you can determine the average dew point conditions within the cargo hold itself. The other options are incorrect because they do not represent the appropriate location for measuring the average cargo hold dew point temperature.