Customer Officer: May I have your declaration from, please?

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Customer Officer : Sure. Please open your suitcase.

(Is the expression 'suitcase' correct in this situation? Do you have some other suitable expressions? Correct the errors, plese.)

In your first sentence, the word needs to be "form" not "from" -- this is a typo I make all the time, and I have to be very conscious of it since a spell-checker will never pick it up!

The use of the word "suitcase" is correct. You could also use "briefcase" or "attache" or "valise" or "bag."

In the United States, the term, "Customs Officer," is more likely to be used.

In this situation, the term "suitcase" is not the most suitable expression. The correct term to use would be "luggage" instead. Luggage is a broader term that encompasses different types of bags and items that can be carried while traveling.

However, if you want to be more specific about the type of bag, you can use terms such as:

1. Carry-on bag: a small bag that is allowed to be taken onboard an airplane.
2. Checked bag: a larger bag that needs to be checked-in and placed in the cargo hold of an airplane.
3. Backpack: a bag worn on the back, typically with two straps.
4. Duffle bag: a large cylindrical bag made of cloth with a drawstring closure.

Remember to adapt the language to the situation and your specific needs when interacting with a customer officer.