In case you think that DIvI' has lots of consonants grouped together: the second and fourth letters are capital i's, not lowercase L's, so it's consonant-vowel-consonant-vowel-consonant (since the final apostrophe represents a consonant sound in Klingon).
Pay careful attention to the little curl at the bottom of the last letter in Hol which marks it as a small L, and the absence of that little curl in the capital i's in DIvI'.
So the word order shows literally [English language what (is)], but then we put it into our word order "What is English?" or "What is the English language?" if that last were acceptable, is it? It does seem unlikely to ask about English if you already know it is a language.
Can we also ask "What is the Federation Standard?"
"What is the English language?" was not on the list of acceptable translations, but I think it should be accepted and have added it now.
"What is Federation Standard?" is also accepted - note, without article, as "Federation Standard" is considered a proper noun (the name of the language) and, like "English", takes no "the" in front of it.