Answer:
D.Identity property of addition
Explanation:
We are given that an expression

Where x is real number .
Identity property of addition: If we add zero to any number then we will get the number .
Suppose a is any number

The property used here is called identity property.
Identity property of multiplication:

Commutative property:

Distributive property:

Hence, option D is true.
Answer: D.Identity property of addition