求问TPO8 第三篇阅读的总结题

vanstaraUID: 3540062

Answer choices
○Mars’ runoff and outflow channels are large-scale, distinctive features that suggest that large quantities of liquid water once flowed on Mars.
○Although some researchers claim that Mars may once have had oceans, others dispute this, pointing to an absence of evidence or offering alternative interpretations of evidence.   
○Various types of images have been used to demonstrate that most of Martian surface contains evidence of flowing water.
○The runoff and outflow channels of Mars apparently carried a higher volume of water and formed more extensive networks than do Earth’s river systems.
○There is very little evidence of liquid water on Mars today, and it is assumed that all the water that once existed on the planet is frozen beneath its surface.
○While numerous gullies have been discovered on Mars since 2000, many astronomers dismiss them as evidence that Mars once had liquid water.

不明白为什么不选various types of……那一句，是因为文中没有用到various  types of images，而是只用到了一种image么？