Multiple choice The movement of the Rongbuk glacier caused the valley to _______. erode evaporate evaporation erosion Reveal answer Fill a bubble to check yourself A Correct answer Explanation The structure 'caused [something] to' must be followed by the base form of a verb. 'Erode' is the correct verb form here. 'Erosion' and 'evaporation' are nouns, and 'evaporate' does not make sense in the context of a valley and a glacier.