"to roam" instead of "to stalk"

[Romano]

Synonym Search, Intermediate level

ESL/EFL Test #109 "Synonyms for walk and go", question 10

The poor boy ......... the fields all alone looking for some privacy.

(a) stalked
(b) roamed
(c) prowled
(d) strayed

Synonym Search, Intermediate level

ESL/EFL Test #109 "Synonyms for walk and go", answer 10

The poor boy roamed the fields all alone looking for some privacy.

Correct answer: (b) roamed

Your answer was: incorrect
The poor boy stalked the fields all alone looking for some privacy.
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Please, explain me why I need to use the verb "to roam" instead of the verb "to stalk" in such situation?

Romano

[Mister Micawber]

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To roam is to wander widely, as one would do when trying to avoid others.

To stalk is to walk stiffly (as if emotional) or to look for prey, as a predator does. This kind of walking is not appropriate to the situation in the test sentence.
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Native English teacher at Mister Micawber's