**Category:** Calculus  
**Subtype:** Function Analysis  
**Problem Description:** Determine the interval where the function \(y=f(x)\) is decreasing based on its graph.  

**Options:**  
A. \((0 ;+\infty)\)  
B. \((-\infty ; 1)\)  
C. \((2 ;+\infty)\)  
D. \((0 ; 1)\)