Dreams often involve sudden emotional reactions and surprising changes in scene. this best serves to support the theory that dreams a represent the brain's attempt to interpret random neural activity. b. provide a summary of the previous day's events. c. reflect one's level of cognitive development. d. represent our failures and current fears.

a. represent the brain's attempt to interpret random neural activity.  

Explanation:

If dreams often involve sudden emotional reactions and surprising changes in the scene, it means that dreams play a cognitive role. To clarify what this role is, one must first construct the notion that dreams reflect some sort of random neural processing. This is because deep brain regions actually promote during REM sleep a seemingly disorganized electrical bombardment of the cerebral cortex.

  b.

there are isolated pockets of farming, generally around rivers and oases, which are used for irrigation.