Why is it inaccurate to say that daydreaming is a total waste of time?

Why is it inaccurate to say that daydreaming is a total waste of time?
 
  a. Because synaptic pruning, which is essential to the overall health of the brain, occur at higher rates during moments of daydreaming.
  b. Because daydreaming gives our brain an opportunity to capture more of the essential REM waves needed for repair and growth.
  c. Because we often think about past experiences and plan our future when the DMN is active during daydreaming.
  d. Because daydreaming gives the brain an opportunity to replenish its supply of spent neurotransmitters, particularly dopamine and serotonin.