Step 1: Match primitive subsistence farming.
This old method uses simple tools like hoes and digging sticks, and its typical form is slash and burn cultivation, so I matches c.
Step 2: Match intensive subsistence farming.
Practised on small plots in crowded regions, it depends heavily on manual labour to raise output, so II matches d.
Step 3: Match commercial and plantation farming.
Commercial farming leans on machines and modern inputs with comparatively little manual labour, matching III with a, while plantation farming grows one crop like tea or coffee across a large area, matching IV with b.
Step 4: Combine and answer.
Putting these together gives I-c, II-d, III-a, IV-b, which is option C.