The correct answer is B. When you want a longer quotation from the text to support an argument in your essay.
Step-by-step explanation
An essay is a type of text with the general purpose of exposing and arguing, in which an author reflects, talks, evaluates, or analyzes a topic of her choice. In the essays, quotes from reliable sources are used to support the arguments that the author gives on the chosen topic, for the author has different options to cite, one of them is the paraphrasing where he/she says in his own words what the source argues; Another way to cite is to use a small fragment of the chosen source, and one of the most used is the blockquote that has more than forty words taken literally from a text that is put in a separate paragraph. Therefore, a block quote is a way to back up an argument with a long quote. So the correct answer is B. When you want a longer quotation from the text to support an argument in your essay.