The major groups of activities for improving crop yields can be classified as :
A. Crop variety improvement

B. Crop production improvement

C. Crop protection management

D. All of these

For A- Depends on finding a crop variety that can give a good yield. Variety can be selected by breeding for various useful desirable characters.

For B- crop production depends upon many factors such as:

(i) Understanding how crops grow and develop.

(ii) Effect of various nutrients, climate, and water on growth of the plant.

(iii) Modification and management of each factor for increasing the yield of the crop

For C- Protecting the crops from weeds, harmful pesticides etc.

Hence all three points are the major groups of activities for improving crop yields.