Amrita's special tree is referred to as a "Friend".

Explanation:

Introduction:
- Amrita has a special tree in her life.
- The question asks how she would refer to this tree.

Option Analysis:
a) Father:
- Father is a term used to refer to a male parent.
- A tree cannot be considered a father as it does not possess the characteristics of a parent.

b) Brother:
- Brother is a term used to refer to a male sibling.
- A tree cannot be considered a brother as it does not possess the characteristics of a sibling.

c) Friend:
- Friend is a term used to refer to someone who is trusted, supportive, and provides companionship.
- A tree can be considered a friend as it can provide shade, shelter, and a peaceful environment.
- Amrita may spend time near the tree, talk to it, and feel a sense of companionship.
- The tree may also provide a sense of comfort and support to Amrita, making it a friend.

d) Mother:
- Mother is a term used to refer to a female parent.
- A tree cannot be considered a mother as it does not possess the characteristics of a parent.

Conclusion:
- Based on the given options, the correct answer is option 'C' - Friend.
- Amrita's special tree is like a friend to her, providing shade, shelter, companionship, and comfort.

Friend