What does "turn himself off" mean?

[Sipa2008]

English Language Tests, Intermediate level

ESL/EFL Test #234 "Phrasal Verbs used with Criminal Activity", question 3

After one-year, Ben decided to .......... He couldn't live with the guilt any longer.

(a) turn himself in
(b) turn himself off
(c) turn down
(d) turn over

English Language Tests, Intermediate level

ESL/EFL Test #234 "Phrasal Verbs used with Criminal Activity", answer 3

After one-year, Ben decided to turn himself in. He couldn't live with the guilt any longer.

Correct answer: (a) turn himself in

Your answer was: incorrect
After one-year, Ben decided to turn himself off. He couldn't live with the guilt any longer.
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What does turn himself off mean?

sipa

[Linda]

The phrase "Turn himself in" refers to a person who tells authorities about a crime he/she has committed. For example, if a person commits a crime and then reveals the truth about what they have done to the proper authorities, he/she has "turned himself/herself in."
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[Torsten]

Hi Sipa,

In addition to Linda's answer I'd like to point out that "turn himself off" is not a commonly used expression.
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