(2012浙江卷) According to scientists, our mental abilities begin to______ from the age of 27 after reaching the highest level at 22.
Everything was perfect for the picnic ______ the weather.
Don’t promise anything ______ you are one hundred percent sure.
We’ll have a picnic in the park this Sunday _________ it rains or it’s very cold.
There were some chairs left over _____ everyone had sat down.
For many cities in the world, there is no room to spread out further, _______ New York is an example.