Answer : C
Explanation:
Relative
adverb is a word or phrase that is used to introduce a clause that tells us
more about a noun.
Here in this case, it is in reference to "the house" and the correct relative adverb is "where".
"where" is used for referring places.
"that" is used to refer to a specific thing/person.
"which" is generally used for things/inanimate objects.
"when" is used to reference to time.
Therefore the correct complete sentence is :
That's the house WHERE I was born.