We let them see each other for a while each day and have even put each on different sides of a glass door , and while she now appears to understand there 's another member of the family , she has n't accepted him and looks at him very angrily . He 's only been here for two days so I hope that when he grows a bit ( he 's so tiny , he does n't meow he squeals ! )
According to the above context, choose the best option to answer the following question.
Question: Who might be on one side of the glass door ?
Options:
- A sibling
 - A kitten
 - A puppy
 - A baby


A kitten