Instructions: In this task, you are given a sentence and question which can be answered using the sentence. Your task is to answer the question using the information from the sentence. The answer to the question is unique and it is a continuous text span from the sentence.
Input: Sentence: For use in icy ground , up to 18 rubber pads can be replaced by the same number of grousers , which are stored in the vehicle 's bow when not in use . 
 Question: why would something be replaced  by something?
Output:
For use in icy ground