Concept:The total supply of land is fixed, but land available for agriculture can be enlarged by making unusable or dry land fit for farming.
Explanation:Land reclamation converts swamps and wastelands into useful farmland.
Irrigation supplies water to dry areas and makes them cultivable.
Mechanised farming only increases output from existing land, not the land supply itself.
A higher price of land cannot create additional physical land.
Thus, reclamation and irrigation are the effective ways to increase agricultural land supply.
Answer:B. reclamation and irrigation