Question

At _____ equator, sunrise occurs at the same time each day.
A. an
B. a
C. the
D. no article

Answer 1

Hint: Articles define the nouns as nonspecific or specific. Nouns are further classified into definite and indefinite articles. Articles are the words ‘a’, ‘an’, and ‘the’. Articles behave like an adjective; it modifies the noun by describing it as specific or non-specific.

Complete answer:
Articles are the words that define if something is specific or unspecific. Articles are classified into two types: definite and indefinite articles.

A definite article is an article that associates a noun to one particular thing. ‘The’ is the definite article which defines its noun as something specific. For example, a definite article is used with something unique, something which was mentioned previously or is known, or something which is identified by the speaker.

For instance, in the sentence ‘please give me the book’
The speaker here refers to the specific book hence with the noun ‘book’ we use a definite article.

Indefinite articles are used in two forms i.e., ‘a’ and ‘an’. We use the indefinite article to refer to a general idea. Indefinite article ‘a’ is used with words that begin with consonants and ‘an’ is used with the words that begin with vowels.

In the above-given sentence, ‘At _____ equator, sunrise occurs at the same time each day.’ the most appropriate word will be option C. the.
In the given sentence we talk about a specific line on the planet Earth. Had we used indefinite articles it would have referred to any unspecific line of Earth. Hence, to specify which line and place we use the definite article ‘the’.

Other options are incorrect as:
Option A. an, is an indefinite article that is used to refer to something in general. The Equator is a line on the earth which is not real but a place where day and night are at equal length. Also, ‘an’ as an indefinite article is used with a word that begins with a vowel letter or a sound of the vowel.
Option B. A is also an indefinite article. We use this reference to something in general and words that begin with a consonant letter
Option D. that, is used to refer to the object which is not near the speaker or something that is not present in the moment.

Additional information:
 We use indefinite article ‘an’ not just with a word that begins with a vowel but also with the word whose initial sound of the letter is a vowel. For example- an honorable woman, an FBI agent.
In both, the phrase the words ‘ honorable’ and ‘FBI’ has the initial sound of vowels ‘o’ and ‘a’ respectively.

Hence the correct answer is option ‘C’.

Note: We do not use indefinite articles with plural or uncountable nouns. A/articles follow the sound of the letter and not just the written letter. Hence, before using the indefinite article we must know the pronunciation of words and note if the initial letter makes the sound of vowels (a,e, i,o,u).