It was rude ______ you to stare at the foreigner when he passed by just now.
The discussion ________ alive when an interesting topic was brought in.
My mind wasn't on what he was saying,so I'm afraid I ________ half of it.
All the preparations for the task ________,and we're ready to start.
Selecting a mobile phone for personal use is not an easy task because technology ________ so rapidly.
Visitors ________ not to touch the exhibits.