1. He memorized it.
He memorized it, didn't he?
Who memorized it?
What did he memorize it?
Did he memorize it?
Did he or she memorize it?
2. They disappointed him.
They disappointed him, didn't they?
Who disappointed him?
Did they disappoint him.
Did they or we disappoint him.
Whom did they disappoint?
3. She practised it.
She practised it, didn't she?
Who practised it?
Did she practise it?
Did she or he practised it?
What did she practise?