The correct option is C i, ii, iv, vi
Crop improvement is done for following factors:
1. Higher yield: To increase the productivity of the crop per acre.
2. Improved Quality: quality is very important in order to overcome malnutrition. It varies from crop to crop.
3. Resistance to biotic and abiotic conditions: Biotic factors involve all kinds of pests whereas abiotic factors involve salinity, drough , water logging etc. Resistance to these stresses can improve crop production.
4. Maturity duration: crops maturing in less time are more desirable.
5. Wider adaptability: Crops should be able to survive in different climatic conditions.
6. Favourable agronomic characteristics: like more foliage for fodder plants.