In 1957, the european economic community broadened the common market to cover additional goods. between member countries were eliminated.
a. imports
b. exports
c. free trade
d. customs duties

So, all you need to know to do this exercise is to understand that the purpose of the Community was to "broaden the common market".

Now, what is needed in order to broaden a common market? if you eliminate something, it should be the Customs duties (the answer is d) - all the other options are needed in a common market!

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