You Are Visiting an Agricultural Area Where the Annual Grain

You are visiting an agricultural area where the annual grain crops are suffering from a drought; the leaves are wilted and yellowing. You notice that alongside the fields some of the trees have leaves that are still green, and measurements show they are transpiring normally. You hypothesize that this is MOST likely because:

A) trees can store water in their large root systems, and so they should switch from annual grains to tree crops like nuts.
B) the root systems of trees extend over a wider area, and so can exploit pockets of available water over a larger area.
C) trees have stronger walls in their xylem conduits and so can withstand higher tensions capable of pulling more water from the same soils than crops.
D) tree roots can extend deep enough to reach groundwater even in dry areas, suggesting that an irrigation well might find a deep source of water and make it available to the crops.