story: The old farmer had two mules and one plow. Both mules like pulling the plow for the farmer. Each day the farmer worried about which mule to used. One morning he saw both mules standing together. He got the idea to hooked both mules to the plow.
 selected sentence: Each day the farmer worried about which mule to used.
The farmer worries about which mule to use >Causes/Enables> The farmer uses both mules