When group members withhold their reservations and criticisms for the sake of consensus, they are engaging in:

a. expressive leadership

b. group solidarity

c. laissez-faire decision making

d. groupthink?

This is an example of D. groupthink.

Groupthink refers to a phenomenon where members of a particular group will do anything in order to keep the peace and harmony within that group. So even if they don't agree with the ideas of other members, they won't say anything so as not to disturb the peace.