Difference between close out and shut out

[helder]

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

I'm afraid that tree will have to come down as it ......... out the light in the sitting room.

(a) close
(b) closes
(c) shut
(d) shuts

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

I'm afraid that tree will have to come down as it shuts out the light in the sitting room.

Correct answer: (d) shuts

Your answer was: incorrect
I'm afraid that tree will have to come down as it closes out the light in the sitting room.
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hello!
i would like to know why in this situation you have used shut out instead of close out.
thank you, for your attention

[Alan]

Shut out is used here because it is more definite and means that no light comes through.
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English as a Second Language
You can read my ESL story Relative Pronoun