Which of the following is NOT a characteristic of hard coal?

Hard coal, often referred to as anthracite, is known for several distinct characteristics. The key attributes that define hard coal include a high carbon content, which typically exceeds 86%, making it one of the most efficient and clean-burning fossil fuels. Its use in electricity generation is prevalent due to its efficiency and high energy output. Another defining feature is its long burning duration, as hard coal burns at a higher temperature and more steadily compared to other forms of coal, such as lignite or sub-bituminous coal.

The choice indicating that hard coal is "soft and crumbly" does not align with its actual properties. Hard coal is dense and has a hard texture, distinguishing it from softer coals that may break apart easily. Thus, the option that states hard coal is soft and crumbly is indeed not a characteristic of hard coal.