Listing completions automatically

[PT]

I'd like to offer the user a list from which she has to select an item.  
Since the user doesn't know what items are on the list the possible items  
should be shown immediately.

I tried using completing-read, but it seems the user has to press TAB at  
least once to have the list of possible completions actually diplayed.

Is there way to show the list immediately?

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