Q. I witnessed . . . . . . . . accident this morning. . . . . . . . . car crashed into . . . . . . . . tree. . . . . . . . . driver of . . . . . . . . car wasn't hurt, but . . . . . . . . car was badly damaged.

Explanation by: Mr. Dubey

The noun 'accident' is an indefinite, singular noun that begins with a vowel, hence the indefinite article 'an' is used. The second and third nouns, 'car' and 'tree' are not specified and they're mentioned for the first time, they're indefinite nouns. Both 'car' and 'tree' begin with a consonant, hence 'a' is the correct article for both. The noun 'driver' has not been mentioned before, but in the context of the sentence, the noun is specific because the driver belongs to that particular car and there can be only one single driver in one car. Hence the reader knows which driver is being spoken about, which is why 'the' is used. In the second sentence the noun 'car' is used twice. By then, we know which specific car is being referred to, hence 'the' is the correct article.