That woman, . . . . . . . . you saw, was my auntie. A. who B. whose C. whom D. which

The correct answer is: A. who

The word “who” is used to refer to people. In this sentence, “who” is used to introduce a relative clause that modifies the noun “woman.” The relative clause tells us something about the woman: that she is the speaker’s aunt.

The other options are incorrect because they are not used to refer to people. “Whose” is used to refer to things that belong to people. “Whom” is used to refer to people as the object of a verb or preposition. “Which” is used to refer to things.

Here is a diagram that shows how the sentence can be parsed:

[That woman] [who you saw] [was my auntie].

The subject of the sentence is “that woman.” The verb is “was.” The object of the verb is “my auntie.” The relative clause is “who you saw.” The relative clause modifies the noun “woman.”

I hope this explanation is helpful!