Which of the following best describes "harshly bitter"?

The term "harshly bitter" is most accurately described by the word "acrid." Acrid refers to a strong and unpleasant smell or taste, often sharp and biting, which aligns well with the notion of something being harshly bitter. This term suggests a quality that is not just bitter but also harsh and intense, evoking an overwhelming sensory experience.

On the other hand, the other choices do not convey the same intensity or characteristics associated with "harshly bitter." For instance, "sour" generally describes a tangy or acidic taste, which is not necessarily harsh. "Neutral" implies the absence of strong flavors altogether, and "sweet" directly opposes the idea of bitterness, indicating a pleasant taste rather than a harsh experience. Thus, "acrid" effectively captures the essence of being harshly bitter.