Elle voit la fin de la route (of the road) L'exterieur du batiment est sale (of the building)
Why is one de la and the other du ?
Hey Patricia! You see in french prepositions usually fit the gender of the verb, (almost like conjugation in a way.)
du (+ masculine word)
de la (+ feminine word),
de l’ (followed by a vowel)
So, du was used because the word is masculine and de la because it's feminine. Hopefully this helped! :)