Which statement regarding the following code is true?

In the context of the code provided, the statement that "mouse.bird.size is not valid" is correct because it assumes that there is an object called mouse, which contains a property called bird, that in turn contains a property called size. For this expression to be valid, all three of these properties must exist and be accessible in the object structure. If either mouse does not have a property named bird, or if bird does not have a property named size, then accessing mouse.bird.size would lead to an error or an undefined value.

The other statements involve using bracket notation, which allows for dynamic access of properties. The second statement, mouse[bird.size], is valid if bird is an object defined somewhere in the code that includes a numeric or string property named size. The third statement, mouse[bird["size"]], also follows the same logic and is valid if bird has a property size. Both bracket notations provide flexibility to access properties, unlike dot notation which requires the property names to exist within the designated object structure.

Therefore, the correct answer reflects the need for a direct, valid path to access the properties involved in