Explanation:

Any method which helps the soil to retain more organic matter , so that it may work as an effective Carbon sink would be helpful in Carbon sequestrian or storage.
Contour Bunding:
Contour bunding Contour bunding is one of the extensively used soil and water conservation technique in several rainfed areas. Contour bunding is a mechanical measure which minimizes the soil erosion. Contour bunding involves the construction of small bunds across the slope of the land along a contour so that the long slope is reduced to a series of small ones. The contour bund acts as a barrier to flow of water down a slope and thus the benefit is that it increases the time so that water concentrates in an area and this more water is absorbed. The question is; whether the contour bunding helps in carbon sequestrian or not . The answer is YES. Contour bunding increases the water holding capacity while minimizing the surface evaporation. Then soil erosion is minimized, and surface residues favour the nutrient recycling and result in higher carbon storage in the soil. This is a correct option.
Relay Cropping:
Relay cropping means that new a crop is planted or sown before the previous one is harvested. This can provide advantages for both crops as one of them may provide nitrogen, shade, support or may discourage pests. The obvious benefit of Relay cropping is soil conservation. Then, relay cropping helps in better yield and also helps in solid conservation. It does help in Carbon Sequestrian. This is also a correct answer.
Zero Tillage:
Zero tillage is also based upon the premise of soil conservation, basic premise is to minimize the disturbances to the soil leading to an increase in retention of water, nutrients and topsoil itself. No-till has carbon sequestration potential through storage of soil organic matter in the soil of crop fields.