Answer: The answer is (d) i and ii only.
Explanation: Weathering refers to the breakdown of rocks and minerals into smaller pieces by physical, chemical, and biological processes. Erosion refers to the movement of these weathered materials by wind, water, or ice.
In scenario (i), lichens growing on boulders are breaking down the minerals in the rock, which is an example of weathering. There is no movement of the weathered materials, so erosion is not occurring.
In scenario (ii), sand settling to the riverbed is an example of erosion, but there is no indication that the sand is being weathered in the process.
In scenario (iii), wind blowing against a cliff face is causing sediment to fall to the ground, which is an example of erosion. However, there is no indication that the sediment is being weathered in the process.