单项选择题

TEXT C
Venus, one of the four inner planets of our solar system, is the closest body in the sky apart from the Moon, sometimes coming only 40 million km from the Earth. Thus, in the not- so-distant future, when man has colonized the Moon, he will start looking at Venus as his next step into space.
As it is now, Venus’s environment is totally unfavourable to human life. Its surface temperature is almost 480℃. Its face is almost completely hidden from view by poisonous clouds of 90% carbon dioxide.
But scientists have a simple plan which, they predict, could make Venus habitable.
With the help of rockets, they plan to bombard the carbon dioxide clouds with colonies of blue-green algae. Experiments carried out on Earth have proved that blue-green algae can survive and reproduce normally in such an environment. The algae will consume the carbon and liberate the oxygen. They reproduce so quickly that the carbon dioxide could be broken down within one year. After that, the surface of Venus will be partly visible to telescopes on Earth.
The increase in oxygen will have spectacular effects on the desert planet. As oxygen re- places the carbon dioxide, the sun’s infra-red radiation, which up to that moment was trapped under the clouds of carbon dioxide, will escape into space and the temperature of the lower atmosphere will decrease. Soon, water will collect from the atmospheric vapor and rain will start falling for the first time. That first rain will never reach the surface. It will vaporize into steam high up in he Venusian atmosphere, but it will have a very important effect. It will lower the ground temperature, perhaps by 35℃. Soon the rain will fall again and again, until the ground temperature is about 70℃. Then the "Big Rain" will strike the soil of Venus for the first time and the clouds will partly clear away, leaving an oxygen-rich atmosphere and a temperature cool enough to sustain hardy plants and animals from Earth.
Which of the following is the most appropriate title for the passage