Last week when we talked about landslides, we looked at what causes these huge masses of earth to move down the natural incline such as a mountainside or slope with such destructive force. Now when these landslides occur in populated areas, what can humans do to avoid or minimize damage? Basically there are three things that can be done. The first thing is to simply avoid construction in the areas where landslides are likely to happen. Typically when a side on the slope is chosen for new construction, it is important that a geological survey of the area be conducted. The survey reveals unsafe conditions such as too little vegetation or soil that would absorb water too easily, conditions that might lead to a landslide, say, during periods of heavy rains. The second thing is to build in a way that doesn't make
stable slopes unstable. For example, natural vegetation, like grass, is needed to keep soil firmly in place. This vegetation should not be entirely removed since without the grass the soil would loosen up and this could result in a land-
slide. The third thing is to design good water drainage to ensure that the water naturally runs down the slope and doesn't build up in the soil. This kind of water buildup on the slope is one of the most frequent causes of landslides. Water buildup can easily result during long periods of heavy rain and sometimes the cause is part of the construction itself such as a stonewall that blocks the water from draining off the slope.
解析
According to the professor, why is it important to perform geological surveys?
细节题。教授指出it is important that a geological survey of the area be conducted．The survey reveals unsafe conditions such as too little vegetation or soil that would absorb water too easily．即“对该地区进行地质勘查是很重要的，调查会揭示一些不安全环境，如植被太少或太容易吸收水分的土壤”。因此，正确答案是B。