Sure, here is the exercise with the appropriate words underlined:

1. We took a guided tour of the historical landmarks in the city.
2. Her voice was so soothing that it put me to sleep.
3. I enjoy reading books in my free time.
4. I am sure that I left my keys on the kitchen counter.
5. The tracker identified the spoor of the wild animal in the forest.
6. The tourist took pictures of the famous monument as a keepsake.
7. He won the chess tournament after many intense matches.
8. Can you please point out the direction to the nearest grocery store?

Now, let's underline the words as per the instructions:

1. We took a guided __tour__ of the historical landmarks in the city.
2. Her __voice__ was so soothing that it put me to sleep.
3. I enjoy reading books in my free time.
4. I am __sure__ that I left my keys on the kitchen counter.
5. The tracker identified the __spoor__ of the wild animal in the forest.
6. The __tourist__ took pictures of the famous monument as a keepsake.
7. He won the chess __tournament__ after many intense matches.
8. Can you please point out the direction to the nearest grocery store?