Here are the odd ones out for each set:

1. **singer** - The odd one is **B. trumpet** (singer is a person; trumpet is an instrument).
2. **occasion** - The odd one is **B. drum** (occasion is not a musical item; drum is).
3. **guitar** - The odd one is **B. paintbrush** (guitar is a musical instrument; paintbrush is for painting).
4. **clown** - The odd one is **C. microphone** (clown is a performer; microphone is a tool).
5. **theatre** - The odd one is **C. performance** (theatre and cinema are places for performances; performance is an action).

Feel free to ask if you need more clarification!