All of the following are causes for groupthink except the belief that the group can do no wrong the belief that the group is invulnerable the belief that those who oppose the group have no worthwhile opinions openness to differing opinions

The correct answer is
openness to differing opinions

Groupthink is basically ignoring the facts just to be able to preserve the group. Often, differing opinions are ignored because they would be bad for the group so you just ignore them in order to preserve cohesiveness of the group. All the other things are causes for groupthink.

There is lots of evidence