eli whitney was an american inventor best known for inventing the cotton gin. this was one of the key inventions of the industrial revolution and shaped the economy of the antebellum south.
the pronoun reference replaces a noun, but you have to make sure there's no room for confusion.
in the first sentence "her" could be referring to shely or to the sister. the answer there is "shelly called her sister and told her about the new baby."
in the second sentence "it" could be referring to the roof or the floor. the answer there is "since the roof leaks on the family room floor, we need to repair the roof."
where is the
greywater is gently used water from your bathroom sinks, showers, tubs, and washing machines. it is not water that has come into contact with feces, either from the toilet or from washing diapers. greywater may contain traces of dirt, food, grease, hair, and certain household cleaning products.