The Reason the Supreme Court Created the Qualified Immunity Defense

The reason the Supreme Court created the qualified immunity defense for police officers is:
I. to protect the broad discretion they need to do their job effectively
II. to prevent officers and courts from being deluged with frivolous lawsuits
III. to discourage citizens from suing the police
IV. to minimize the public's knowledge about police misconduct

A) I, II
B) I, II, III, IV
C) I, III, IV
D) III