Translation:Are klongats dangerous? Yes. Klongats are very dangerous.
It's wrong in Standard American English. There are dialects of English in which Klongats be dangerous would be perfectly grammatical, Black English for one. But this course only accepts Standard American English, with occasional allowances for British English, and in SAE, you must conjugate be in places like this.
Qob'a' tlhonghaDmey has tlhonghaDmey as the subject, so tlhonghaDmey are doing something. The thing they are doing is represented by the verb, Qob be dangerous. The -'a' means you're asking a yes/no question regarding their being dangerous. In Standard American English, you'd ask this as Are klongats dangerous? and that's the response the course is expecting. In Standard American English, you typically must put the be verb at the beginning for yes/no questions, and you must conjugate the verb. The correct conjugation of be for a third-person plural subject is are. Then you state the subject, then the adjective.