late Middle English (denoting the sense of smell): from Old French sentir ‘perceive, smell,’ from Latin sentire . The addition of -c- (in the 17th century) is unexplained.
So the c is silent and also shouldn't really be there
english language " pronunciation" and "spelling" are ridicilous... don't worry about it. (c is silent but without making any sense) ( I know this is a joke, and I am NOT joking, that's my JOKE)