In a business cycle, the underuse of resources typically occurs during the trough and the recession phases. The trough is the lowest point of the cycle, characterized by low economic activity and high rates of unemployment, leading to underutilization of resources. Similarly, during a recession, economic activity slows down, resulting in decreased production and higher unemployment, which again leads to underutilization of resources. The peak represents the highest point of economic activity, and recovery is the phase where economic activity begins to increase again, thus not marked by underuse of resources.