It is very likely that the part previous to this passage is about ______.

A．It requires genuine police skills.
B．It can be justified.
C．It is crucial for the solving of a crime.
D．It over-estimates the police role but ignores the informant Y s role.

A．The climate in recorded human history has generally remained stable.
B．The climate from about 135,000 to 115,000 years ago was in a extremely cold state.
C．The human race has been lucky to have enjoyed the most favorable period of climate for them to build a socio-economic system.
D．The evidences scientists collected from the ice cores suggest that a civilization can not have arisen in the period from about 135,000 to 115,000.