A vertical disc plough (also called a harrow plough or one-way disc plough) combines the principles of a regular disc plough and a disc harrow. Its discs are mounted on a single common gang axle with a fixed tilt angle of zero (vertical discs) and disc angle typically $35^\circ$ to $50^\circ$, operating at shallow depths ($8\text{ to }12\text{ cm}$). Option analysis: (A) Vertical disc plough is the exact implement combining disc plough and disc harrow features. (B) Chisel plough breaks hardpans without inversion. (C) Sub-soiler operates deep ($\gt 45\text{ cm}$) to shatter subsoil. (D) Standard disc plough has individually mounted tilted discs.

Statement (A) is false: puddling destroys soil aggregates, disperses clay particles, and DRASTICALLY REDUCES soil shear strength and bearing capacity of the puddle layer. Statement (B) is true: puddling creates a dense subsurface hardpan reducing percolation losses. Statement (C) is true: fine clay soils puddle much more readily than sandy soils. Statement (D) is true: puddling is specific to transplanted wetland rice. Hence (B), (C), and (D) are true. Option analysis: (A) Statement (A) is false. (B) Omits statement (B). (C) (B), (C) and (D) only is the correct answer. (D) Contains false statement (A).

Area of one hectare $= 10,000\text{ m}^2$. Width of cut of country plough $W = 15\text{ cm} = 0.15\text{ m}$. Total distance walked is $D = \frac{\text{Area}}{W} = \frac{10,000\text{ m}^2}{0.15\text{ m}} = 66,666.67\text{ m} = 66.67\text{ km} \approx 66.7\text{ km}$. Option analysis: (A) $30.3$ is incorrect. (B) $45.6$ is incorrect. (C) $66.7\text{ km}$ is the exact calculated distance. (D) $60.5$ is incorrect.