Sunday pressure

A, throwing a coin and landing backwards is a random event, which does not meet the meaning of the question;

B, Sunday must be sunny, random events, does not meet the meaning of the question;

C, under the standard atmospheric pressure, water will boil when heated to 100, which is an inevitable event and conforms to the meaning of the question;

D, turn on the TV, the cartoon is playing, which is a random event and does not meet the meaning of the question.

So choose C.