根据以下资料，回答19~22题。 It is possible that the weather of the world may be changing．S

ome scientists imagine that this could even mean the beginning of another ice age．The effects of such a change in weather on human population of the world would be frightening. Recent research suggests that the warming trend (倾向 ) of the past hundred years or so may be coming to an end．During the past ten years, scientists tell us that the temperature of the world has dropped a little．This would have effects on wind and rain in the weather picture. Scientists believe clouds may be an important factor (因素) in changing the amount of heat on the earth．Another possibility is that man's agriculture and industry ways may affect the natural weather. The weather of the world seems to be getting __. A．hotter B．colder C．warmer D．freezing