Choose the term that best fits this group of words. a fern reproduces through spores a. exclamatory sentence b. imperative sentence c. fragment d. declarative sentence

Your answer would be D. DECLARATIVE SENTENCE, mainly because it declares or states something. These don't ask questions, make commands, or make statements with emotion.
The reason it isn't any of the other answers is because, it's not an exclamatory sentence because it doesn't end with an exclamation point, nor does it convey that kind of emotion. It's not an imperative sentence, because those types of sentences end in an exclamation point, and usually appear demanding, nor is it a fragmented sentence, because a fragment sentence fails to be a sentence in the sense that it cannot stand by itself.

The answer is

Because the vietnam war was fought in an especially brutal and untraditional way