a) Starting at the outer end
b) Starting at the centre
c) Back furrowing
d) Starting at the outer end & starting at the centre

Answer: d
Explanation: In starting at the centre method a small plot of land is marked in the middle of the field and it is ploughed first. After that, the plough works round this small plot and the entire plot is completed. In starting at the outer end tractor starts ploughing at one end of the field and then moves on all sides of the plot and comes gradually from the sides to the centre of the field.