Which window style features two operable sashes?

The correct answer is double hung, as this window style is specifically designed with two vertically sliding sashes that open independently. Each of these sashes can be moved up and down, allowing for flexibility in terms of ventilation and airflow. Homeowners can choose to open either the top or bottom sash, making double hung windows versatile for various weather conditions.

The other window styles mentioned serve different functions. Casement windows, for instance, are hinged on one side and open outward, typically providing good ventilation but with only one operable sash. Picture windows are fixed and do not open at all, primarily used for ample views and natural light without the need for ventilation. Sliding windows have sashes that slide horizontally, which can include one or more operable sashes, but they do not feature the traditional vertical operation seen in double hung windows.