Compared with other species, why are social connections especially important for the survival of ...

Compared with other species, why are social connections especially important for the survival of human beings?
 
  a. Human beings typically lose the drive to survive during times of prolonged isolation.
  b. Human beings require the greatest amount of parenting to survive to adulthood and reproduce.
  c. Human beings have a set point for social activity and need external connections to monitor the balance.
  d. Human beings suffer both psychological and physical damage from isolation, whereas most other species are unaffected by it.