The correct answer is: D. no article
A tiger is a striped animal.
The article "a" is used before singular nouns that refer to a general or unspecified thing. For example, "I saw a tiger in the zoo."
The article "the" is used before singular nouns that refer to a specific or particular thing. For example, "I saw the tiger that escaped from the zoo."
In the sentence "A tiger is a striped animal," the word "tiger" is not being used to refer to a specific or particular tiger. It is being used to refer to tigers in general. Therefore, the article "a" is not necessary.
