Answer:
Option A - 0.73
Step-by-step explanation:
Given : The probability of a certain event occurring is 0.27 →P(A)=0.27
To find : The probability that the event will NOT occur → 
Solution: Since we know the sum of probability is 1
According to rule of complement → 
P(A)= 0.27 , put value we get



Therefore, option A is correct
Probability that the event will not occur= 0.73