Events A, B and C cover the entire space of events and are DISJOINT (= mutually exclusive).
THEREFORE
(a) P(C) = 1 - P(A) - P(B) = 1 - 0.990 - 0.001 = 0.009.
(b) P = P(B') = 1 - P(B) = 1 - 0.001 = 0.999.
(c) P = 1 - P(A) = 1 - 0.990 = 0.01.