The probability of a certain event is
The correct option is C $$1$$
A certain event means an event which is sure to happen.
The probability of a certain event is 1.
For example, "Getting a number less than 7 when a fair dice is rolled" is a certain event.
A dice has $$1,2,3,4,5 \ and \ 6$$ printed on it. So, we are sure that whatever comes will be less than 7. So, we thus conclude that the probability of a certain event is $$1$$