Peter, Paul and Mary Have Just One Weekend to Climb

Peter, Paul and Mary have just one weekend to climb a famous mountain. Early on the first morning the weather does not look too good, and individually they know they can't climb that day. So they sit in their cabin to talk about what comes next. Five minutes later, they know. They will tackle the climb the next day, whatever the weather. This looks suspiciously like an instance of:

A) diffusion of responsibility.
B) conformity.
C) follow-the-leader.
D) groupthink.