21. — Jay Chou is in our city. Let’s go and watch his show this Saturday.— That’s great, but I need to call my dad and ask for _________ before I go out.
. So many people wanted to go to the game that another train had to be ______.
. The dictionary published by Oxford University Press recently has really ______ because it is of great use to the learners of English.
. There were no tickets _____ for Friday's performance.
. Today, housework has been made much easier by electrical _____.