IS
1. William is excited about his promotion
2. The professor is absolutely sure.
3. The tomato is rotten.
4. My brother is mad when he’s hungry.
5. The company is true to its founding principles.
ARE
1. My friends are dancing at Stella’s tonight.
2. The girls are happy because they’re eating all together.
3. Ambitions are good if your efforts are worthy.
4. We are dismayed about the foreclosure.
5. We are the champions!