appropriate/proper/suitable

[angliholic]

I don't think T-shirt and blue jeans are appropriate/proper/suitable clothes for this occasion.



Do all of the underlined words fit in the above wording? If not, why not? Thanks.

[Anglika]

They all fit neatly.

[cisco795]

Greetings.
Are there any differences among these words in every day`s English?
How could one distinguishibly use all of them without hesitation?

The following sentences will show my doubts (My native language is Spanish):

"Should it be appropriate/proper for us to ask?"
"That book is not appropriate/suitable for young readers"
"I do not think your behave is appropriate/proper"
"what is the proper/apprpriate usage of these sentences"
"Countries will soon start using proper/appropriate custom measures at their airports"

Thanks in advance for your help.
God bless you all.
Cisco.