What function can social supports serve in a client's life?

What function can social supports serve in a client's life?
 
  a. Social supports can buffer the negative impact of stressors and help with the
  client's environmental problems such as global warming, natural disasters,
  and lack of housing and transportation
  b. Social supports can mediate the severity of some problems, moderate
  favorable and positive effects of various psychosocial problems and serve as
  protective factors that buffer the negative impact of stressors
  c. Social supports can serve as protective factors that enhance the negative
  impact of stressors, mediate the severity of some problems and moderate
  positive effects of various psychosocial problems
  d. Social supports can serve as protective factors that buffer the negative impact
  of stressors, mediate the severity of some problems and moderate adverse
  effects of various psychosocial problems