The correct answer is option 1, co-operative farming. Co-operative farming refers to agricultural production where resources and labor are shared among a group of farmers. It is actually considered as a potential solution to increase productivity in agriculture.

Option 2, inadequate inputs availability, can indeed be a cause of low productivity. This refers to the lack of essential resources like seeds, fertilizers, pesticides, and machinery, which can hinder agricultural output.

Option 3, sub-division and fragmentation of land holdings, can also contribute to low productivity. When land holdings are divided into smaller plots, it becomes inefficient to use modern farming techniques and larger machinery, leading to lower yields.

Option 4, poor finance and marketing facilities, can also be a cause of low productivity. Limited access to credit, insurance, and market infrastructure can prevent farmers from investing in better technologies and obtaining fair prices for their produce.