Inter-cropping is the practice of growing two or more crops together in a field. It is done in order to maximize the productivity of the land, as well as to improve the overall crop yield.

Option 1: This option is incorrect. Inter-cropping is not related to the time period between two cropping seasons.

Option 2: This option is incorrect. Inter-cropping is not about randomly mixing different crops together. It involves specific row patterns or arrangements.

Option 3: This is the correct answer. Inter-cropping involves growing different crops in definite row patterns. This arrangement allows each crop to have sufficient space, sunlight, and nutrients for growth and development.

Option 4: This option is incorrect. Inter-cropping is not about growing different crops in a pre-planned succession. It refers to the simultaneous cultivation of different crops together.

In conclusion, inter-cropping is the practice of growing different crops in specific row patterns in order to optimize land productivity and crop yield.