**Solution:**

(i) Two complementary events, taken together, include all the outcomes for an experiment and the sum of the probabilities of all outcomes is 1.

P(A) + P(B) = 1

(ii) P(A) = 0.46

Let P(B) be the probability of not happening of event A

Then we know that,

P(A) + P(B) = 1

P(B) = 1 – P(A)

P(B) = 1 – 0.46

P(B) = 0.54

Thus, the probability of not happening of event A is 0.54