In the Americans’ minds, there are boundaries that other people are simply not supposed to cross. When the boundaries are crossed, Americans will（ ） stiffen and their manner will become cool.
I thought the children（ ）when we returned home, but they were still awake.
Colorado state lawmakers will debate a bill, which will treat cyber-bullying as（ ）.
Nobody knows（ ） how many people are to be blame for the coal-mine accident, so the government is trying to find out the whole truth about the accident.
______ evidence that language-acquiring ability must be stimulated.
The servant is not used to（ ）like a slave.