The correct answer is D, no article.
The word “elephant” is a common noun, which means it refers to a general class of things, not a specific thing. Common nouns are not typically preceded by articles.
In this case, the speaker is asking if the listener has seen a tiger and an elephant together. The speaker is not asking about a specific tiger or elephant, but about tigers and elephants in general. Therefore, the word “elephant” should not be preceded by an article.
Here are some other examples of common nouns that are not typically preceded by articles:
- dog
- cat
- house
- car
- tree
- flower
Note that there are some exceptions to this rule. For example, common nouns can be preceded by articles when they are used in a specific context. For example, you might say “I saw a dog” if you are talking about a specific dog that you saw. You might also say “the dog” if you are talking about a specific dog that you know well.
In general, however, common nouns are not typically preceded by articles.