Final answer:
Option d.
Sedimentary rocks are classified into detrital, chemical, and organic types based on their origin and the processes involved in their formation. The correct option that aligns with this classification is 'detrital, chemical, or organic'.
Step-by-step explanation:
Sedimentary rocks are classified based on their formation process into three major types: detrital, chemical, and organic.
Detrital sedimentary rocks form from weathered and eroded particles that are transported and deposited in layer forms.
Chemical sedimentary rocks are formed from the precipitation of minerals from water, commonly in bodies of water where evaporation occurs, leaving behind mineral deposits.
Lastly, organic sedimentary rocks result from the accumulation of organic debris, creating materials such as coal, oil, and natural gas.
The option that best fits this classification scheme is 'd. detrital, chemical, or organic'. Therefore, the final answer to the question 'Sedimentary rocks are usually classified as ____.' is Option d.