Hi Molly. If the answer was positiveness, we’d need the article in front as it’s a noun. I saw it as a positiveness As Dan says, the answer is positive, as that’s an adjective to go with the noun changes. The changes are positive.

The relation between "positive" and "positiveness" is the same as the relation between "happy" and "happiness". The first is an adjective and the second is a noun. Both would be grammatically correct in #23. However, #23 does not just ask for a "correct" answer. It asks for the *best* correct answer, and that would be the adjective "positive". Let's look at a simpler example with "happy" and "happiness": "It pleased Linh's grandma that she was happy." "Linh's happiness pleased her grandma." A noun would not be wrong in #23: "Linh's grandma interprets the smell in the air as pollution."

I think you mean 23. She sees the changes in a certain way, that calls for an adjective. Also, I dont think 'positiveness' is a word--at least I've never heard it. Okay, I just looked it up, and it is a real word, but it's not very common. Anyway - the sentence structure needs an adjective.