The correct answer would be b. crop management.
Crop management is one way to achieve sustainable agriculture. It refers to the group of agricultural practices which helps in improving the development, growth, and yield of the crops.
It considers all the aspects of the whole farm such as soil management, site selection, crop rotation, its nutrition, water management, pest management, and landscape management as per local climate and other conditions.
It also includes environmental and socio-economic factors in order to provide the safest and suitable approach for long-term benefits.