Identify the correct abstract noun to complete each sentence from the options provided (or infer if none are provided).

Here are the correct abstract nouns to complete each sentence:

1. My friendship with Reena goes back many years.
2. It takes patience to learn painting.
3. The house was in complete darkness.
4. It was a pleasure to meet all my friends.
5. We must reduce the wastage of paper.
6. Nihal wants to apply for library membership.