动词填空。
1. Many of the world's inventions have__________ __(creat) simply by surprise.
2. Ben _____________(promise) to keep the secret, so he wouldn't tell anyone even though asked to.
3. He ___________(discover) a pot in the ground.There were 32,000 Chinese metal coins.
4. Ann (practise) colour therapy since she left college.
1, been created 2. promised
3. discovered 4. has practised