题目选项分析

In the arid land along the Colorado River, use of the river's water supply is strictly controlled：farms along the river each have a limited allocation that they are allowed to use for irrigation.But the trees that grow in narrow strips along the river's banks also use its water.Clearly, therefore, if farmers were to remove those trees, more water would be available for crop irrigation.

Which of the following, if true, most seriously weakens the argument?

【选项】The trees along the river's banks shelter it from the sun and wind, thereby greatly reducing the amount of water lost through evaporation.