Write in the plural.

1. It's a funny story.
- They're funny stories.

2. She's a pretty woman.
- They're pretty women.

3. He's a famous businessman.
- They're famous businessmen.

4. Look at the white cat.
- Look at the white cats.

5. You're a smart girl.
- You're smart girls.

6. It's an interesting activity.
- They're interesting activities.

To write the sentences in plural form, you need to change both the subject and the main elements of each sentence from singular to plural. Here's how you can do it:

"She's a pretty woman."
- Plural: "They're pretty women."
- Explanation: "She is" changes to "They are" and "woman" changes to "women," as 'woman' is the singular form and 'women' is its plural.
"He's a famous businessman."
- Plural: "They're famous businessmen."
- Explanation: "He is" becomes "They are," and "businessman" changes to "businessmen," which is the plural.
"Look at the white cat."
- Plural: "Look at the white cats."
- Explanation: "Cat" changes to "cats," the regular plural form of the noun.
"You're a smart girl."
- Plural: "You're smart girls."
- Explanation: "Girl" becomes "girls," indicating more than one.
"It's an interesting activity."
- Plural: "They're interesting activities."
- Explanation: "It is" is replaced with "They are," and "activity" becomes "activities," by adding -ies to convert the singular form to plural.

By understanding how to convert each element in a sentence from singular to plural, you can write sentences correctly in their plural form. This involves adjusting both the subject (or pronoun where applicable) and the nouns being described. Always be sure to use the correct plural form of words, which can sometimes be irregular like "woman" to "women."