What do floodplains, sandbars, and river deltas have in common?

They've all been formed by water erosion

Explanation:

Water erosion is referred to as the detachment and transport of materials in the form of soil particles or movements of soil mass from one location to another on the action of rain and runoff. Its negative effects are associated with delicate equilibrium regions whose soil is very susceptible to erosion. The lack of vegetation cover, together with the characteristics of the precipitation, are factors that interfere in this process with intensity and frequency. In addition to causing soil loss, water erosion is one of the main elements forming floodplains, sandbars and river deltas.

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.