How to use "agreement" in a sentence

"Because your son is still seventeen, we need your official agreement, please."

But I believe that this is best for all of us." He looked over at Dani, who nodded in agreement

Bob shook his head in agreement, frowning, as if he was dismayed to think that he could be mistaken for a common thief.

By unspoken agreement, Tina and Elliot didn't talk about their problems while they ate

He looked at the wet night and gave a short bark of agreement.