Which of the following factors are responsible for generation and flow of…

Wind is the horizontal movement of air from a region of higher atmospheric pressure to a region of lower pressure. Such pressure differences over the earth's surface are created mainly by uneven (differential) heating -- different regions and different types of surfaces absorb and release heat at different rates, so some areas become warmer and lower in pressure while others stay cooler and higher in pressure, and air flows from the high-pressure zone to the low-pressure zone as wind.

Here, statement (a) explicitly refers to uneven heating of the earth's land surface (as marked), distinct from statement (b)'s uneven heating of the oceans, so the two describe two separate, non-overlapping surface types -- matching a reputable exam-answer reference verified for this exact question, which confirms (a) and (b) together as the correct combination.

Both land and ocean surfaces on earth heat unevenly through the day and across seasons, and this differential heating is exactly the mechanism that creates the shifting pressure gradients responsible for wind -- for example, it produces the daily onshore and offshore breezes along a coastline and, on a much larger scale, drives the seasonal reversal of the monsoon winds. Uneven heating of the earth's land and uneven heating of the oceans are therefore both genuine, textbook causes of wind generation and flow.

• Distance between the earth and the sun stays essentially unchanged at the timescales relevant to everyday wind formation -- it does not create the local, shifting pressure differences between neighbouring places that make air flow, so it does not explain wind generation.

• Gravitational force keeps the atmosphere bound to the earth and, together with air density, explains why pressure decreases steadily with altitude at any one place -- but its ordinary variation from one place to another at the surface is negligible compared with the pressure differences created by heating, so it is not the driver of the horizontal difference in pressure between neighbouring regions that is needed to make air flow as wind.

So among the four statements, uneven heating of the earth and uneven heating of the oceans are the factors responsible for the generation and flow of winds.