A watch uses two electronic circuits (ECs). Each EC has a failure probability of 0.1 in one year of operation

Q. A watch uses two electronic circuits (ECs). Each EC has a failure probability of 0.1 in one year of operation. Both ECs are required for functioning of the watch. The probability of the watch functioning for one year without failure is

(A) 0.99                      (B) 0.90                      (C) 0.81                      (D) 0.80

Ans: 0.81