While colleges look at your overall GPA and academic record, a single D won't necessarily prevent admission. Colleges consider many factors, including:
* Overall GPA: A few D's amongst mostly A's and B's will have a less significant impact than a transcript full of D's and F's.
* Course rigor: Taking challenging courses (AP, IB, honors) demonstrates ambition, even if your grades aren't perfect in those classes. A D in a challenging class might be viewed more favorably than an A in an easy class.
* Trends: Is the D an anomaly, or part of a downward trend? Improving grades show colleges you're capable of growth.
* Explanatory factors: Was the D due to a temporary setback (illness, family emergency)? Explaining extenuating circumstances in your application materials can be helpful.
* Extracurricular activities, essays, letters of recommendation: These demonstrate other aspects of your abilities and character.
In short, a single D is unlikely to be a deal-breaker, but consistently poor grades will significantly reduce your chances of admission to a selective four-year college. The *specific* class in which you received the D matters less than the overall picture your transcript paints.