Being under his care, it was his duty to keep it in good condition.
Robert shrank from informing him, but he knew it to be his duty, and he was too brave to put it off.
He hates to go, but he says it's his duty; the call is so loud.
She had her duty to perform, and she expected to be taken care of till it was done.
All have done their duty well, and to them also I desire ...