Not supported, because the author never suggests groupthink occurs in “all” highly cohesive groups. In fact, the author indicates that high cohesion alone is not sufficient for groupthink.

Not supported, because the researchers have identified groupthink as a “recurring pattern” that involves specific factors. These factors aren’t unique to each individual case of groupthink. If they can be identified as a recurring patter, that suggests these factors appear across different cases.

Not supported, because the author think additional research is “important” for determining when high cohesion results in groupthink.

Too strong. Although groupthink involves worse decisionmaking due to group members' lack of critical scrutiny of group decisions, we don’t know that outside information cannot influence group decisions. Perhaps outside information can influence group decisions — the group as a whole makes a decision based on outside information, and individual group members don’t critically evaluate the decision.

Supported, because the author views groupthink as negative — she uses the word “deteriorate” and “pitfall” to describe what happens when a group exhibits groupthink. In addition, researchers identify groupthink as involving “excessive optimism” and “closed-mindedness to warnings of problems.” It’s reasonable to think the researchers believe these things are negative.