Final answer:
Antonio Zadra is not surprised when the middle-aged man he had studied winds up divorcing because he had observed and analyzed evidence and behavior that led him to anticipate the divorce based on the expected marriage disappointment.
Step-by-step explanation:
Antonio Zadra is not surprised when the middle-aged man he had studied winds up divorcing because he had observed and analyzed evidence and behavior that led him to anticipate the divorce. This can be seen in the line 'she had been expecting him, and expecting to be married for fourteen years, but she was as much surprised and taken aback as if she had never thought of it.' Zadra had likely noticed signs of unhappiness or problems in the man's marriage, which would have led him to predict the divorce.