Answer:
Option b - not significantly greater than 75%.
Step-by-step explanation:
A random sample of 100 people was taken i.e. n=100
Eighty of the people in the sample favored Candidate i.e. x=80
We have used single sample proportion test,



Now we define hypothesis,
Null hypothesis
: candidate A is significantly greater than 75%.
Alternative hypothesis
: candidate A is not significantly greater than 75%.
Level of significance 
Applying test statistic Z -proportion,

Where,
and 
Substitute the values,




The p-value is



Now, the p-value is greater than the 0.05.
So we fail to reject the null hypothesis and conclude that the A is not significantly greater than 75%.
Therefore, Option b is correct.