Which is not a true statement regarding individual and group decision making

Which is not a true statement regarding individual and group decision making
 
  a) The best decision maker in a group usually can not make a better decision alone than with the entire group
  b) Group decisions can be more costly in terms of staff time than individual decisions
 
  c) When the group solves intellectual tasks, members' rational, information-processing orientation maybe impeded by socioemotional concerns
  d) Part of the superiority of group problem solving results from the pooling of individual judgments to converge on a group norm.