"I can read it."
If jI is first person singular, why is it, this time, vI?
This is explained in the tips and notes for the first unit, 'Useful phrases'. Perhaps you want to go back and re-read them: https://www.duolingo.com/skill/kl/Useful-phrases/tips-and-notes . (In particular, the section "Verbs".)
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Basically, Klingon prefixes identify not only the subject, but also the object or lack of object.
See the tips and notes for details.
If, after reading them, there is still something incomprehensible, incomplete, or contradictory, please comment here and we can try to help you further.