7.
阅读理解
As is known to all, the world's highest mountain, Qomolangma, is 8848.86 metres high. And this number has been kept in mind by people for really a long time. But in fact, not all people agree on this number and you need to forget it now. Different researchers have given different results. Also, the height(高度)of the mountain can change over time because of earth movements like earthquakes or plate drifting (板块漂移). That is the reason why a 30-member Chinese survey (测量)team set out to reach the top of Qomolangma to survey its height all over again on May 6, 2020.
But is a difference of a few metres so important when it comes to a high mountain? In fact, surveying the height of Qomolangma means more than just getting an exact number. Mount Qomolangma came into being around 38 million years ago as the Eurasian plate and the Indian plate hit each other heavily. The change of its height shows whether the two plates are heading toward or away from each other. In addition, knowing the mountain's changes can guide us to better do some national projects including road and railway building.
On May 28, the team reached the mountain top. But it was not easy for them to do the task there. The average (平均的)air temperature on the mountain top is- 29℃ - four degrees lower than that in Antarctica (南极洲). And powerful winds blow all the time. In such bad conditions, drones (无人机)aren't able to work as usual. It is still necessary for the country to send human surveyors to get exact results, though it means risking their lives.
One of the surveyors said, "It will probably take two to three months to get the exact height of the mountain because of the difficulties. We will also get information about environmental conditions on the mountain top, which will help understand environmental changes have influenced our earth.