open vs shut vs close

[rich7]

Test No. incompl/inter-10 "Close/Shut", question 3

The detectives had no problems in solving the crimes as it was clearly an open and ......... case.

(a) closed
(b) closing
(c) shut
(d) shutting

Test No. incompl/inter-10 "Close/Shut", answer 3

The detectives had no problems in solving the crimes as it was clearly an open and shut case.

Correct answer: (c) shut

Your answer was: incorrect
The detectives had no problems in solving the crimes as it was clearly an open and closed case.
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I've always wondered why open and not opened? and also why in heaven in this case is open and shut. if you see answer n5
it reads a" closed case. it doesn't add up....

Thanks

[Alan]

Here the words are used in an adjectival sense and in Number 5 clearly this is a verbal constuction to be closed. Consider the expression have an open mind.
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[rebecca]

Hi there,
I don't understand clearly about shut and close?
can you help me?
thanks
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