To change an assertive sentence to an interrogative sentence, you typically need to rephrase the sentence to pose a question. Here are the rephrased sentences for each of the given assertive sentences:
1. She is beautiful.
- Interrogative form: Is she beautiful?
2. They were playing a match.
- Interrogative form: Were they playing a match?
3. The guest planted the tree.
- Interrogative form: Did the guest plant the tree?
By adding auxiliary verbs (such as "is," "were," and "did") and rearranging the sentence structure, we can transform assertive sentences into interrogative sentences that ask a question. This change helps in seeking information or confirming a fact in a conversation or written text.