The correct answer is C. A dispute before a court may be called <u>an</u> action.
Explanation
The indefinite article is the name of a group of articles that are used to refer to something that is not definite, for example when I say "I see a dog", "You see an airplane", "they sing a song", among others. On the other hand, there are Definite articles, that is a name of articles which are used to refer to something that is definitely for example "I see the dog", "You see the airplane", "they sing the song" or others. According to the above, the phrase with an indefinite article (an, or a) is C. A dispute before a court may be called an action.
