Swahili, like Russian, Turkish, and several other languages, doesn't have articles. Almost any time a noun is presented, a/ an and the should both be accepted. As well as no article as long as it is not required grammatically in the English sentence. So in this instance (using sour instead of strong) Acid is sour. The acid is sour. An acid is sour. All three should be accepted. The Swahili sentence doesn't (and really can't, due to the language structure) indicate whether the word is generalized or not.