Step 1: Understanding the Question:
This question requires choosing an appropriate adjective that logically connects with the consequence of making it ``difficult for his friends to trust him.''
Step 2: Key Concepts and Vocabulary Definitions:
The key phrase in the sentence is ``difficult... to trust him''.
Trust is damaged or hard to build when someone's behavior is unpredictable, inconsistent, or unreliable.
We need an adjective with a negative or unstable connotation that explains this difficulty in establishing trust.
Step 3: Detailed Explanation:
• Option (A) - adjustable: This means flexible or capable of being modified. This is generally a positive quality and does not lead to distrust.
• Option (B) - erratic: This means not even or regular in pattern or movement; unpredictable. An erratic attitude directly causes a lack of trust because people cannot predict how the person will behave. This fits the blank perfectly.
• Option (C) - acceptable: This means satisfactory or pleasing. This is a positive attribute and would make trusting a person easier, not harder.
• Option (D) - amicable: This means characterized by friendliness and goodwill. Friendly and amicable behavior fosters trust rather than hindering it.
Step 4: Final Answer:
Thus, the word that best fits the logical requirement of the context is ``erratic'', corresponding to Option (B).