Computational Complexity for Searching Problem

Goal: We what to determine what is the of the best possible searching algorithm (in the worst-case).

For any searching algorithm, we can draw a decision tree. The following decision tree is for binary searching of an array S with 7 elements and a target of x.

1) What are the general characteristics of decision trees for search algorithms that compare elements?

2) What part of the decision tree represents the worst-case behavior for searching?