Fill in the blank with the correct or no article:
I have a black and ________ white dog.
(There are two dogs of which one is black and the other is white)
(a) a
(b)an
(c)the
(d)No Article

Hint: Read the given sentence and decipher what it means. Now go through the given options and understand what they signify. You can use the hit and trial method to see which of the options fit the context of the sentence while keeping it grammatically correct.

Complete answer: Articles are the words that tell us whether a noun is specific or unspecific. They're categorised as definite and indefinite articles. In the above question, the speaker is talking about possessing two dogs; one being black and the other being white. Hence, we’ve to complete the sentence using an appropriate article.
Definite Articles are used when we talk about something specific or the fact that is already talked about. There’s only one definite article namely: “The”.
Indefinite Articles are used when the situation or the thing is unspecific or the thing which we’re not aware of. There Are two indefinite articles; “a” and “an”.
Now, let us analyze the given options: Option(a) “a”, it is used before the words that produce consonant sound. Since “white dog” too starts with a consonant sound and furthermore it is singular in nature. Hence, Option(a) is correct.
Option(b) “an”, it is used before the words that start with vowel sound. In the question above, “white dog” starts with a consonant sound. Hence, this option becomes invalid.
Option(c) “the”, it is a definite article, which is usually used with the specific nouns, in the question we are not aware of which white dog is talked about. Hence, option(c) “the” is incorrect.
Option(d) “No article”, this option comes into effect when we talk about uncountable nouns, but in the question “white dog” is countable. Hence, this option is incorrect.
therefire, option a is the right answer.

Note: The definite article “the” can be used with singular as well as plural nouns and with uncountable nouns too, but indefinite articles “a” and “an” are used with singular nouns only. Uncountable nouns are the nouns that can not be counted and mostly include intangible things.