Why we cannot say : "he is not skilled" . How can i say it ?
po'be' does indeed mean He is not skilled.
Did you enter that and it was graded as wrong? It is one of the accepted answers. Do you have a screen shot so we can see if we can tell what went wrong?
I am not sure I entered that, no screen :/ thanks to your response :-)
In all other places before, we are encouraged to translate these prefixless verbs as "he/she/it does X", but here the main translation is the English infinitive. What gives?
If you look carefully, you may see that there is no period on this one. It is not a sentence, but a dictionary word. But it's easy to miss a small punctuation difference like that, so the complete sentence is also accepted as a translation.
Klingon has no infinitive, so translating into English infinitive is a poor choice. What they're trying to do is translate just the word, not in a sentence. They should probably leave off the to.