Consider the following nested representation of Binary Trees (ASD) where S and D are left and right subtrees of node A. Note that S and D may be NULL or further nested.
In this scenario, which of the following representation is a valid Binary Tree?
- $(12(4567))$
- $(1((234)56)7)$
- $(1(234)(567))$
- $(1(23 \text{NULL} )(45))$