The diagram is a schematic representation of the electron transport mechanism in mitochondria

There are several reasons why there will discrepancies between the budget and the actual amount for expenditures and revenues. These differences can occur because of the strength of the economy, consumer needs or preferences and the actions of competitors

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.