In English, the adjective in front of the noun is the reason, so a or an? He is an excellent student. Or he is an excellent student? He is a skilled operator?

Look at the first phoneme after "a" and "an", use "an" for vowels and "a" for consonants
He is an excellent student.
He is a skilled operator.

RELATED INFORMATIONS

1. On the usage of a (an), and, noun and adjective If I want to say a simple, simple love It's a simple and a honest love, right Or a simple and honey love If you add a comma before and, like a simple, and (a) honey love, is there a second a?
2. English compound noun + noun, adjective + noun Please give me an example!
3. English adjectives: what are the characteristics of adjectives formed by adding - between two nouns Why add ed sometimes?
4. Is it right to add an article before an adjective and a noun after an adjective
5. After using some, do the countable nouns need to be plural?
6. Whether to add a countable noun after some or an uncountable noun,
7. When so and such modify the plural of nouns, for example, which do so beautiful flowers and such beautiful flowers use? These are such beautiful flowers that we all want to pick them
8. What does it mean that other can't be used alone? Some people like to stay at home on Sundays, but others like to go to the cinema
9. Is there a plural noun after "other"? Can we add plural nouns after other? What about others?
10. Can I use the plural noun + the plural noun
11. Examples of "quiet / rather + A / an + Adjective + noun"
12. Is the article before "Adjective + noun" a, or an? Whether the article in front of "Adjective + noun" uses a or an depends on the adjective or noun
13. So that = such that
14. Some English questions (about some nouns, adverbs, adjectives...) Prepare, feel Happy, lucky adverbs, nouns, antonyms Adjectives of wonder, taste, cloud Antonyms of kind, poor, hopeful, useful, helpful, able, interesting Smile, set, feel gerund Past tense of smile, taste, set, feel The antonyms of interest are comparative and superlative
15. How to distinguish adjective adverb from countable noun in English Not from translation
16. The conversion of some English nouns, adjectives and adverbs For example, success successful
17. Which words can be used to add ly directly when adjectives change into adverbs
18. How to change adjective adverb NOUN
19. What are the rules of nouns changing into adjectives and adverbs in English?
20. What is the general rule of nouns changing into adjectives and adverbs in English?