Concept:
In Reading Comprehension or Logical Inference, a "definitely true" statement must be supported by the explicit facts mentioned in the text without making outside assumptions.
Step 1: Evaluating the premises of the passage.
The parents say: "a rabbit would not be comfortable in a
small house."
This is the reason given for refusing the rabbit.
Step 2: Testing the conclusions.
The text explicitly links the rabbit's comfort to the
size of the house.
Therefore, it is definitely true that
Aarav and his parents live in a small house.
Options (A), (B), and (D) are assumptions. We don't know if they "like" fish more, or if Aarav "dislikes" them, or if they plan to move. Only (C) is a fact provided in the context.