The correct option is B It complicates written matter, by including a variety of sentence types.
Sentence variety means using an assortment of sentences, including their types, varied lengths and different rhythms. Sentence variety is used to make a passage sound more enriching. Too much of any type of sentence makes the passage monotonous, hence a shift in the pattern is required. If you read sentences that are all lengthy, you will lose focus. If you read too many exclamatory sentences huddled together, you will not take the matter seriously. Too many short sentences make the passage look childish. Hence using this explanation, options A, C and D are relevant to sentence variety. Since we have to choose the option that is irrelevant, these are incorrect. Option B is correct because it does not state the true purpose; sentence variety does not complicate matter, it makes it simpler to read and comprehend. Hence we choose this option.